Physics Ultimate Exam Trivia!

1. Friction between moving parts of machine causes

Heat

Light

Energy

Oil

Friction between moving parts of a machine causes heat. When two surfaces rub against each other, the friction generated converts mechanical energy into heat energy. This heat can cause the temperature of the machine to increase, which may lead to various consequences such as wear and tear, reduced efficiency, or even damage to the machine if not properly managed or lubricated.

Explanation

Friction between moving parts of a machine causes heat. When two surfaces rub against each other, the friction generated converts mechanical energy into heat energy. This heat can cause the temperature of the machine to increase, which may lead to various consequences such as wear and tear, reduced efficiency, or even damage to the machine if not properly managed or lubricated.

2. Gold-leaf electroscope is used to

Detect the presence of charges on a body

Measure potential differences

Determine the magnetic flux density of a field

Measure current

The gold-leaf electroscope is a device used to detect the presence of charges on a body. When a charged object is brought close to the electroscope, the gold leaves repel each other due to the like charges. This indicates the presence of charges on the body. The greater the charge on the body, the greater the separation of the gold leaves. Therefore, the gold-leaf electroscope is commonly used in experiments and demonstrations to detect the presence of electric charges.

Explanation

The gold-leaf electroscope is a device used to detect the presence of charges on a body. When a charged object is brought close to the electroscope, the gold leaves repel each other due to the like charges. This indicates the presence of charges on the body. The greater the charge on the body, the greater the separation of the gold leaves. Therefore, the gold-leaf electroscope is commonly used in experiments and demonstrations to detect the presence of electric charges.

3. Different types of surfaces create different amount of friction

True

False

Friction is a force that opposes motion and it depends on the nature of the surfaces in contact. Different surfaces have different textures and properties, which can affect the amount of friction they generate. For example, rough surfaces tend to create more friction compared to smooth surfaces. Therefore, it is true that different types of surfaces create different amounts of friction.

Explanation

Friction is a force that opposes motion and it depends on the nature of the surfaces in contact. Different surfaces have different textures and properties, which can affect the amount of friction they generate. For example, rough surfaces tend to create more friction compared to smooth surfaces. Therefore, it is true that different types of surfaces create different amounts of friction.

4. Which of the following material is more elastic?

Rubber

Glass

Steel

Wood

*##*Correct*##*Wrong

Explanation

*##*Correct*##*Wrong

5. Which of the following statements about liquids is correct? They

Are elastic

Contract when heated

Flow

Have definite shape

Liquids have the ability to flow, which means they can move and change shape when a force is applied. Unlike solids, liquids do not have a definite shape and can take the shape of their container. This characteristic allows liquids to flow and adapt to different environments, making the statement "flow" the correct answer.

Explanation

Liquids have the ability to flow, which means they can move and change shape when a force is applied. Unlike solids, liquids do not have a definite shape and can take the shape of their container. This characteristic allows liquids to flow and adapt to different environments, making the statement "flow" the correct answer.

6. Which of the following is NOT a method to reduce friction?

By Lubrication

By Polishing

Throwing sand on the Ground

None of the above

Throwing sand on the ground does not reduce friction; instead, it increases it. When sand is thrown on the ground, it creates roughness and increases the contact area between surfaces, leading to more friction. Lubrication, on the other hand, reduces friction by providing a layer between surfaces, reducing direct contact. Polishing also reduces friction by making surfaces smoother, reducing the roughness that causes friction. Therefore, throwing sand on the ground is not a method to reduce friction.

Explanation

Throwing sand on the ground does not reduce friction; instead, it increases it. When sand is thrown on the ground, it creates roughness and increases the contact area between surfaces, leading to more friction. Lubrication, on the other hand, reduces friction by providing a layer between surfaces, reducing direct contact. Polishing also reduces friction by making surfaces smoother, reducing the roughness that causes friction. Therefore, throwing sand on the ground is not a method to reduce friction.

7. Which one is not a dimension?

Length

Mass

Time

Kelvin

*##*Correct*##*Wrong

Explanation

*##*Correct*##*Wrong

8. A metal rod of length 100cm is heated through 100⁰C, calculate the change in length of the rod. [Linear expansivity of material of the rod is 3 x 10^-5K^-1]

4mm

3mm

2mm

1mm

When a metal rod is heated, it expands due to thermal expansion. The change in length of the rod can be calculated using the formula:

ΔL = αLΔT

Where ΔL is the change in length, α is the linear expansivity of the material, L is the original length of the rod, and ΔT is the change in temperature.

In this case, the linear expansivity (α) is given as 3 x 10-5K-1, the original length (L) is 100cm, and the change in temperature (ΔT) is 1000C.

Using the formula, we can calculate:

ΔL = (3 x 10-5K-1) * (100cm) * (1000C) = 3mm

Therefore, the change in length of the rod is 3mm.

Explanation

When a metal rod is heated, it expands due to thermal expansion. The change in length of the rod can be calculated using the formula:

ΔL = αLΔT

Where ΔL is the change in length, α is the linear expansivity of the material, L is the original length of the rod, and ΔT is the change in temperature.

In this case, the linear expansivity (α) is given as 3 x 10-5K-1, the original length (L) is 100cm, and the change in temperature (ΔT) is 1000C.

Using the formula, we can calculate:

ΔL = (3 x 10-5K-1) * (100cm) * (1000C) = 3mm

Therefore, the change in length of the rod is 3mm.

9. Which of the following has no units?

Thermal capacity

Tensile strain

Acceleration

Impulse

Tensile strain is a dimensionless quantity that represents the change in length of an object divided by its original length. Since it is a ratio of lengths, it does not have any units. The other options, thermal capacity, acceleration, and impulse, all have units associated with them. Thermal capacity is measured in units of energy per degree Celsius, acceleration is measured in units of meters per second squared, and impulse is measured in units of Newton-seconds.

Explanation

Tensile strain is a dimensionless quantity that represents the change in length of an object divided by its original length. Since it is a ratio of lengths, it does not have any units. The other options, thermal capacity, acceleration, and impulse, all have units associated with them. Thermal capacity is measured in units of energy per degree Celsius, acceleration is measured in units of meters per second squared, and impulse is measured in units of Newton-seconds.

10. The instrument of measurement of weight is _____

Beam balance

Spring balance

Lever arm balance

Equal arm balance

A spring balance is an instrument used to measure weight. It consists of a coiled spring that stretches when a weight is attached to it. The amount of stretch in the spring is directly proportional to the weight applied, allowing for an accurate measurement of weight. This makes the spring balance a commonly used tool in various industries and everyday life for measuring the weight of objects.

Explanation

A spring balance is an instrument used to measure weight. It consists of a coiled spring that stretches when a weight is attached to it. The amount of stretch in the spring is directly proportional to the weight applied, allowing for an accurate measurement of weight. This makes the spring balance a commonly used tool in various industries and everyday life for measuring the weight of objects.

11. What volume of alcohol with a density of 8.0 x 10²kgm^-3 will have the same mass as 4.2m³ of petrol whose density is 7.2 x 10²kgm^-3?

1.4 m3

3.6 m3

4.9 m3

5.0 m3

The question asks for the volume of alcohol that has the same mass as 4.2 m3 of petrol. To find this, we need to compare the densities of alcohol and petrol. The density of alcohol is given as 8.0 x 102 kg/m3, and the density of petrol is given as 7.2 x 102 kg/m3. Since the density of alcohol is greater than the density of petrol, we can conclude that alcohol is denser than petrol. Therefore, to have the same mass as 4.2 m3 of petrol, we would need a smaller volume of alcohol. The only option that is smaller than 4.2 m3 is 3.6 m3, so it is the correct answer.

Explanation

The question asks for the volume of alcohol that has the same mass as 4.2 m3 of petrol. To find this, we need to compare the densities of alcohol and petrol. The density of alcohol is given as 8.0 x 102 kg/m3, and the density of petrol is given as 7.2 x 102 kg/m3. Since the density of alcohol is greater than the density of petrol, we can conclude that alcohol is denser than petrol. Therefore, to have the same mass as 4.2 m3 of petrol, we would need a smaller volume of alcohol. The only option that is smaller than 4.2 m3 is 3.6 m3, so it is the correct answer.

12. A sledge is pulled 10m by a force 40N.what is the work done?

400 Nm

650 Nm

657 Nm

740 Nm

The work done is calculated by multiplying the force applied to an object by the distance it is moved. In this case, the force applied is 40N and the distance moved is 10m. Therefore, the work done is 40N x 10m = 400 Nm.

Explanation

The work done is calculated by multiplying the force applied to an object by the distance it is moved. In this case, the force applied is 40N and the distance moved is 10m. Therefore, the work done is 40N x 10m = 400 Nm.

13.

A car fuse marked 3A operates optimally on 12V battery. calculate the resistance of the fuse

3 4Ω

4Ω

6Ω

9Ω

*##*correct*##*incorrect

Explanation

*##*correct*##*incorrect

14. Which of the following statements about matter is not correct

Molecules of solids move more freely than molecules of liquids and gases

Molecules of solids are more closely packed than those of the liquids

Energy is required to break the intermolecular forces of attraction between molecules

Molecules of liquids move about within the liquid and they are in constant random motion

The statement "Molecules of solids move more freely than molecules of liquids and gases" is incorrect. In solids, molecules are tightly packed and have limited movement, whereas in liquids and gases, molecules have more freedom to move and are not as tightly packed.

Explanation

The statement "Molecules of solids move more freely than molecules of liquids and gases" is incorrect. In solids, molecules are tightly packed and have limited movement, whereas in liquids and gases, molecules have more freedom to move and are not as tightly packed.

15. The property of a material by which it can be beaten or rolled into thin sheets, is called

Elasticity

Plasticity

Ductility

Malleability

*##*correct*##*wrong

Explanation

*##*correct*##*wrong

16. An engine raises 100kg of water through a height 60m in 20sec.what is the power of the engine. (g=10m/s²)

8 KW

3 KW

2 KW

1.4 KW

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

17. A rod of initial length 2m at a temperature of 25⁰C is heated to 80⁰C. Calculate the increase in length of the rod if its linear expansivity is 4.0 x 10^-3k^-1

0.26m

0.44m

0.53m

0.84m

When a rod is heated, it undergoes thermal expansion, causing an increase in its length. The increase in length can be calculated using the formula ΔL = αLΔT, where ΔL is the change in length, α is the linear expansivity, L is the initial length, and ΔT is the change in temperature. In this case, the initial length (L) is 2m, the linear expansivity (α) is 4.0 x 10-3k-1, and the change in temperature (ΔT) is 800C - 250C = 550C. Plugging these values into the formula, we get ΔL = (4.0 x 10-3k-1)(2m)(550C) = 0.44m. Therefore, the increase in length of the rod is 0.44m.

Explanation

When a rod is heated, it undergoes thermal expansion, causing an increase in its length. The increase in length can be calculated using the formula ΔL = αLΔT, where ΔL is the change in length, α is the linear expansivity, L is the initial length, and ΔT is the change in temperature. In this case, the initial length (L) is 2m, the linear expansivity (α) is 4.0 x 10-3k-1, and the change in temperature (ΔT) is 800C - 250C = 550C. Plugging these values into the formula, we get ΔL = (4.0 x 10-3k-1)(2m)(550C) = 0.44m. Therefore, the increase in length of the rod is 0.44m.

18. _________ is the instrument of measurement of atmospheric pressure

Micrometer screw gauge

Bolometer

Barometer

Anenometer

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

19. The evidence that matter consist of particles is illustrated by I. Brownian motion II. Diffusion III. Law of definite proportions

I only

I,II and III

II and III

III only

The evidence that matter consists of particles is supported by all three options: I. Brownian motion, II. Diffusion, and III. Law of definite proportions. Brownian motion is the random movement of particles suspended in a fluid, which can only be explained if the particles are individual entities. Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration, which indicates that particles are moving independently. The Law of definite proportions states that a compound always contains the same elements in the same ratio by mass, suggesting that matter is composed of discrete particles. Therefore, all three options provide evidence for the particle nature of matter.

Explanation

The evidence that matter consists of particles is supported by all three options: I. Brownian motion, II. Diffusion, and III. Law of definite proportions. Brownian motion is the random movement of particles suspended in a fluid, which can only be explained if the particles are individual entities. Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration, which indicates that particles are moving independently. The Law of definite proportions states that a compound always contains the same elements in the same ratio by mass, suggesting that matter is composed of discrete particles. Therefore, all three options provide evidence for the particle nature of matter.

20. Which of the following is a not an application of surface tension

Absorption of ink in blotting paper

Rising of oil lamp wick

Movement of melted wax into the neck of a burning candle

Falling of a metal bob through water

The falling of a metal bob through water is not an application of surface tension because surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. It is responsible for phenomena such as capillary action, where liquids can rise in narrow tubes against the force of gravity. However, the falling of a metal bob through water is simply an example of an object sinking due to its own weight and the buoyant force exerted by the water. Surface tension does not play a role in this scenario.

Explanation

The falling of a metal bob through water is not an application of surface tension because surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. It is responsible for phenomena such as capillary action, where liquids can rise in narrow tubes against the force of gravity. However, the falling of a metal bob through water is simply an example of an object sinking due to its own weight and the buoyant force exerted by the water. Surface tension does not play a role in this scenario.

21. A body of mass 4kg moves through a distance 80m, calculate the work done on the body. (g=10m/s²)

6.2 KJ

3.2 KJ

3.0 KJ

1.4 KJ

The work done on an object can be calculated using the formula W = F * d, where W is the work done, F is the force applied, and d is the distance over which the force is applied. In this case, the force applied can be calculated using the formula F = m * g, where m is the mass of the object and g is the acceleration due to gravity. Plugging in the given values, F = 4kg * 10m/s^2 = 40N. The work done is then calculated as W = 40N * 80m = 3200J, which is equal to 3.2 KJ.

Explanation

The work done on an object can be calculated using the formula W = F * d, where W is the work done, F is the force applied, and d is the distance over which the force is applied. In this case, the force applied can be calculated using the formula F = m * g, where m is the mass of the object and g is the acceleration due to gravity. Plugging in the given values, F = 4kg * 10m/s^2 = 40N. The work done is then calculated as W = 40N * 80m = 3200J, which is equal to 3.2 KJ.

22. The dimension of density is __

ML-3

MLT-2

LT-2

LT-1

*##*correct*##*incorrect

Explanation

*##*correct*##*incorrect

23. Two different materials rubbed against each other acquire opposite charges when separated. This is an example of charging by

Induction

Friction

Conduction

Convection

When two different materials are rubbed against each other, the friction between them causes the transfer of electrons from one material to the other. This transfer of electrons results in one material acquiring a positive charge and the other material acquiring a negative charge. Therefore, the statement "Two different materials rubbed against each other acquire opposite charges when separated" is an example of charging by friction.

Explanation

When two different materials are rubbed against each other, the friction between them causes the transfer of electrons from one material to the other. This transfer of electrons results in one material acquiring a positive charge and the other material acquiring a negative charge. Therefore, the statement "Two different materials rubbed against each other acquire opposite charges when separated" is an example of charging by friction.

24. Candela is the unit of …………………

Magnetic flux

Intensity of electric field

Luminous intensity

Charge

Candela is the unit of luminous intensity. Luminous intensity refers to the amount of light emitted or reflected from a particular direction. It is a measure of the brightness of a light source as perceived by the human eye. The candela is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 terahertz and has a radiant intensity in that direction of 1/683 watt per steradian.

Explanation

Candela is the unit of luminous intensity. Luminous intensity refers to the amount of light emitted or reflected from a particular direction. It is a measure of the brightness of a light source as perceived by the human eye. The candela is defined as the luminous intensity in a given direction of a source that emits monochromatic radiation of frequency 540 terahertz and has a radiant intensity in that direction of 1/683 watt per steradian.

25. Calculate the potential energy of Dam if the height is 200m and the mass of the water is 5kg (g=10m/s²)

56 KJ

50 KJ

30 KJ

10 KJ

The potential energy of an object is given by the formula PE = mgh, where m is the mass, g is the acceleration due to gravity, and h is the height. In this case, the mass of the water is given as 5kg, the height is given as 200m, and the acceleration due to gravity is given as 10m/s^2. Plugging these values into the formula, we get PE = 5kg * 10m/s^2 * 200m = 10,000 J = 10 KJ. Therefore, the correct answer is 10 KJ.

Explanation

The potential energy of an object is given by the formula PE = mgh, where m is the mass, g is the acceleration due to gravity, and h is the height. In this case, the mass of the water is given as 5kg, the height is given as 200m, and the acceleration due to gravity is given as 10m/s^2. Plugging these values into the formula, we get PE = 5kg * 10m/s^2 * 200m = 10,000 J = 10 KJ. Therefore, the correct answer is 10 KJ.

26. The stress in a rod is 70 N/mm² and the modulus of elasticity is 2 x 10⁵ N/mm². what will be the strain in the rod?

0.00052

0.00035

0.00030

0.00047

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

27. MLT^-2 is the dimension of ___

Density

Acceleration

Force

Time

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

28. A metal rod of length 50cm is heated from 40⁰C to 80⁰C. If the linear expansivity of the material is ᾳ, calculate the increase in length of the rod (in meters) in terms of ᾳ.

20 ᾳ

200 ᾳ

2000 ᾳ

20000 ᾳ

When a metal rod is heated, it undergoes thermal expansion, causing an increase in its length. The linear expansivity (α) is a measure of how much the length of a material changes with a change in temperature. In this question, the metal rod is heated from 40°C to 80°C. The increase in temperature is 80°C - 40°C = 40°C. The increase in length of the rod can be calculated using the formula ΔL = α * L * ΔT, where ΔL is the change in length, α is the linear expansivity, L is the original length of the rod, and ΔT is the change in temperature. Plugging in the given values, ΔL = ᾳ * 50cm * 40°C = 2000 ᾳ. Therefore, the increase in length of the rod is 2000 ᾳ.

Explanation

When a metal rod is heated, it undergoes thermal expansion, causing an increase in its length. The linear expansivity (α) is a measure of how much the length of a material changes with a change in temperature. In this question, the metal rod is heated from 40°C to 80°C. The increase in temperature is 80°C - 40°C = 40°C. The increase in length of the rod can be calculated using the formula ΔL = α * L * ΔT, where ΔL is the change in length, α is the linear expansivity, L is the original length of the rod, and ΔT is the change in temperature. Plugging in the given values, ΔL = ᾳ * 50cm * 40°C = 2000 ᾳ. Therefore, the increase in length of the rod is 2000 ᾳ.

29. Which of the following is not a physical quantity?

All of the above

Candela

Henry

Kelvin

The question asks for a physical quantity that is not included in the given options. The options include "Candela," "Henry," and "Kelvin." Candela is the SI unit for luminous intensity, Henry is the SI unit for inductance, and Kelvin is the SI unit for temperature. Therefore, the correct answer is "Henry," as it is the only option that does not represent a physical quantity.

Explanation

The question asks for a physical quantity that is not included in the given options. The options include "Candela," "Henry," and "Kelvin." Candela is the SI unit for luminous intensity, Henry is the SI unit for inductance, and Kelvin is the SI unit for temperature. Therefore, the correct answer is "Henry," as it is the only option that does not represent a physical quantity.

30. Which of the following statement is not true

Water wets glass

Mercury wets glass

Cohesion is the forces of attraction between molecules of the same substances or kind.

Adhesion is the force of attraction between molecules of different substances or kind

The statement "Mercury wets glass" is not true because mercury does not wet glass. Wetting is the ability of a liquid to spread out and make contact with a solid surface. Mercury does not wet glass because it forms droplets on the surface instead of spreading out.

Explanation

The statement "Mercury wets glass" is not true because mercury does not wet glass. Wetting is the ability of a liquid to spread out and make contact with a solid surface. Mercury does not wet glass because it forms droplets on the surface instead of spreading out.

31. Which of the following is a scalar quantity

Time

Displacement

Force

Pressure

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

32. Which of the following is not a way of reducing surface tension on water

By adding soaps/detergents

By heating the liquid

By adding sand

By adding kerosene

Adding sand to water does not reduce surface tension. Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. Adding soaps/detergents, heating the liquid, and adding kerosene all reduce surface tension. Soaps and detergents contain molecules that have a hydrophilic (water-attracting) and hydrophobic (water-repelling) end, which disrupts the cohesive forces between water molecules. Heating the liquid increases the kinetic energy of the molecules, weakening the intermolecular forces and reducing surface tension. Kerosene is a nonpolar substance that does not interact strongly with water, reducing surface tension. However, sand does not have any effect on surface tension as it does not interact with water molecules in a way that reduces the cohesive forces at the surface.

Explanation

Adding sand to water does not reduce surface tension. Surface tension is the force that causes the surface of a liquid to behave like a stretched elastic sheet. Adding soaps/detergents, heating the liquid, and adding kerosene all reduce surface tension. Soaps and detergents contain molecules that have a hydrophilic (water-attracting) and hydrophobic (water-repelling) end, which disrupts the cohesive forces between water molecules. Heating the liquid increases the kinetic energy of the molecules, weakening the intermolecular forces and reducing surface tension. Kerosene is a nonpolar substance that does not interact strongly with water, reducing surface tension. However, sand does not have any effect on surface tension as it does not interact with water molecules in a way that reduces the cohesive forces at the surface.

33. In the formation of sea breeze, wind blows from

Sky to land

Sea to sky

Land to sea

Sea to land

Sea breeze is a local wind that occurs during the day near coastal areas. It is caused by the temperature difference between the land and the sea. During the day, the land heats up faster than the sea, causing the air above the land to become warmer and rise. As a result, cooler air from the sea moves in to replace the rising warm air, creating a breeze that blows from the sea to the land. Therefore, the correct answer is "sea to land".

Explanation

Sea breeze is a local wind that occurs during the day near coastal areas. It is caused by the temperature difference between the land and the sea. During the day, the land heats up faster than the sea, causing the air above the land to become warmer and rise. As a result, cooler air from the sea moves in to replace the rising warm air, creating a breeze that blows from the sea to the land. Therefore, the correct answer is "sea to land".

34. A resistor with fixed resistance value is called a

Resistance box

Standard resistor

Shunt

Multiplier

A resistor with a fixed resistance value is called a standard resistor. This term is often used in electrical engineering to refer to a resistor that has a known and precise resistance value, which is used as a reference for measuring and calibrating other resistors or electrical circuits. Standard resistors are typically manufactured and tested to have a very low tolerance, ensuring their accuracy and reliability in various applications.

Explanation

A resistor with a fixed resistance value is called a standard resistor. This term is often used in electrical engineering to refer to a resistor that has a known and precise resistance value, which is used as a reference for measuring and calibrating other resistors or electrical circuits. Standard resistors are typically manufactured and tested to have a very low tolerance, ensuring their accuracy and reliability in various applications.

35. The ice and steam points on a mercury-in-glass thermometer are 10cm and 30cm respectively. Calculate the temperature in degree Celsius, when the mercury meniscus is at the 14cm mark

20 oC

30 oC

34 oC

70 oC

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

36. Land breeze occurs

During the day

As a result of heat transfer by radiation

As a result of heat transfer by conduction

As a result of heat transfer by convection

Land breeze occurs as a result of heat transfer by convection. During the day, the land heats up faster than the water. This causes the air above the land to become warmer and rise, creating a low-pressure area. The cooler air over the water then moves towards the land to fill this void, resulting in a land breeze. Convection is the process of heat transfer through the movement of fluids or gases, and in this case, it explains how the warmer air rises and the cooler air moves in to replace it, causing the land breeze.

Explanation

Land breeze occurs as a result of heat transfer by convection. During the day, the land heats up faster than the water. This causes the air above the land to become warmer and rise, creating a low-pressure area. The cooler air over the water then moves towards the land to fill this void, resulting in a land breeze. Convection is the process of heat transfer through the movement of fluids or gases, and in this case, it explains how the warmer air rises and the cooler air moves in to replace it, causing the land breeze.

37. The following processes are explained by surface tension except

Water rising up a capillary tube

Bristles of a paint brush cling together when removed from water

Spherical droplets of water dropping from a tap

Needle floating on water.

Surface tension is the property of a liquid that allows it to resist external forces and minimize its surface area. It is responsible for phenomena such as the formation of droplets and the cohesion of liquid molecules. However, the process of water rising up a capillary tube is not explained by surface tension alone. This process is mainly due to capillary action, which is the result of adhesive and cohesive forces between the liquid and the walls of the tube.

Explanation

Surface tension is the property of a liquid that allows it to resist external forces and minimize its surface area. It is responsible for phenomena such as the formation of droplets and the cohesion of liquid molecules. However, the process of water rising up a capillary tube is not explained by surface tension alone. This process is mainly due to capillary action, which is the result of adhesive and cohesive forces between the liquid and the walls of the tube.

38. Which of the following is true of the meniscus of mercury in a capillary tube

The meniscus is concave

The meniscus is plano-concave

The meniscus is convex

The meniscus is plano-convex

The meniscus of mercury in a capillary tube is convex. This means that the surface of the mercury is curved upwards at the edges, forming a rounded shape. This is due to the cohesive forces between the mercury molecules being stronger than the adhesive forces between the mercury and the glass of the capillary tube. As a result, the mercury forms a convex shape, with the highest point in the center of the meniscus.

Explanation

The meniscus of mercury in a capillary tube is convex. This means that the surface of the mercury is curved upwards at the edges, forming a rounded shape. This is due to the cohesive forces between the mercury molecules being stronger than the adhesive forces between the mercury and the glass of the capillary tube. As a result, the mercury forms a convex shape, with the highest point in the center of the meniscus.

39. Highly polished silvery surface are

Poor absorbers and poor emitters of radiation

Good absorbers and good emitters of radiaton

Good absorbers but poor emitters of radiation

Poor absorbers but good emitters of radiation

Highly polished silvery surfaces are poor absorbers and poor emitters of radiation because their smooth and reflective surfaces prevent them from absorbing and emitting radiation effectively. Instead, they reflect most of the radiation that comes into contact with them. This property makes them suitable for applications such as mirrors or reflective coatings, where their ability to reflect light is desired.

Explanation

Highly polished silvery surfaces are poor absorbers and poor emitters of radiation because their smooth and reflective surfaces prevent them from absorbing and emitting radiation effectively. Instead, they reflect most of the radiation that comes into contact with them. This property makes them suitable for applications such as mirrors or reflective coatings, where their ability to reflect light is desired.

40. A wire of cross-sectional area 0.60mm² has a resistivity of 7.2 x 10^-7ῼm. Calculate the length of the wire that will have a resistance of 3ῼ.

0.25m

2.50m

3.60m

36.00m

The resistance of a wire can be calculated using the formula R = ρ * (L/A), where R is the resistance, ρ is the resistivity, L is the length of the wire, and A is the cross-sectional area of the wire. Rearranging the formula, we have L = R * (A/ρ). Plugging in the given values, L = 3ῼ * (0.60mm2 / 7.2 x 10-7ῼm) = 2.50m. Therefore, the length of the wire that will have a resistance of 3ῼ is 2.50m.

Explanation

The resistance of a wire can be calculated using the formula R = ρ * (L/A), where R is the resistance, ρ is the resistivity, L is the length of the wire, and A is the cross-sectional area of the wire. Rearranging the formula, we have L = R * (A/ρ). Plugging in the given values, L = 3ῼ * (0.60mm2 / 7.2 x 10-7ῼm) = 2.50m. Therefore, the length of the wire that will have a resistance of 3ῼ is 2.50m.

41. A girl whose mass is 40kg walks up a flight of 20 steps each 150mm height in 10secs.find the average power developed (g=10m/s²)

450 W

325 W

120 W

12 W

The average power developed can be calculated by dividing the work done by the time taken. The work done can be calculated by multiplying the force exerted (which is equal to the girl's weight, given by mass x acceleration due to gravity) by the distance covered (which is equal to the height of each step multiplied by the number of steps). The time taken is given as 10 seconds. Therefore, the average power developed is 120 W.

Explanation

The average power developed can be calculated by dividing the work done by the time taken. The work done can be calculated by multiplying the force exerted (which is equal to the girl's weight, given by mass x acceleration due to gravity) by the distance covered (which is equal to the height of each step multiplied by the number of steps). The time taken is given as 10 seconds. Therefore, the average power developed is 120 W.

42. The body will move only when

Force of friction = applied force

Force of friction < applied force

Force of friction > applied force

All of the above

The correct answer is "Force of friction

Explanation

The correct answer is "Force of friction

43. Which of the following statements distinguishes thermal conduction from convection? I. Conduction requires a material medium while convection does not II. In convection, there is actual motion of hot materials, while in conduction, molecules vibrate faster about there mean positions III. Conduction takes place in solids while convection takes place in fluids.

I and II only

II and III only

I and III only

I, II and III

Statement I is correct because thermal conduction requires a material medium, such as a solid or a liquid, for the transfer of heat. On the other hand, convection does not require a material medium as it involves the actual motion of hot materials, such as fluids, to transfer heat. Statement II is also correct because in conduction, heat is transferred through the vibration of molecules, which causes them to collide with neighboring molecules and transfer energy. In convection, however, there is actual motion of hot materials, such as fluids, which carry heat from one place to another. Statement III is incorrect because conduction can also take place in fluids, such as in the case of heat transfer through a metal rod immersed in a liquid.

Explanation

Statement I is correct because thermal conduction requires a material medium, such as a solid or a liquid, for the transfer of heat. On the other hand, convection does not require a material medium as it involves the actual motion of hot materials, such as fluids, to transfer heat. Statement II is also correct because in conduction, heat is transferred through the vibration of molecules, which causes them to collide with neighboring molecules and transfer energy. In convection, however, there is actual motion of hot materials, such as fluids, which carry heat from one place to another. Statement III is incorrect because conduction can also take place in fluids, such as in the case of heat transfer through a metal rod immersed in a liquid.

44.

If 2 resistors of 5kΩ and 7kΩ are connected in series across a 15V battery, then the current flowing through each of the resistance should be

2 mA

3.6 mA

5 mA

1.25 mA

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

45. The force of friction depends on

Nature of surface of contact

Materials of objects in contact

A & B

None of the Above

The force of friction depends on the nature of the surface of contact and the materials of objects in contact. The nature of the surface of contact refers to whether it is rough or smooth, which affects the amount of friction. The materials of objects in contact also play a role, as different materials have different coefficients of friction. Therefore, both factors, the nature of the surface and the materials of objects, determine the force of friction.

Explanation

The force of friction depends on the nature of the surface of contact and the materials of objects in contact. The nature of the surface of contact refers to whether it is rough or smooth, which affects the amount of friction. The materials of objects in contact also play a role, as different materials have different coefficients of friction. Therefore, both factors, the nature of the surface and the materials of objects, determine the force of friction.

46. The following are crystal except_____

Graphite

Ice

Potassium chloride

Sugar

Sugar is not a crystal because it does not have a regular repeating pattern of molecules or ions in its structure. Graphite, ice, and potassium chloride all have a crystalline structure, meaning their molecules or ions are arranged in a repeating pattern.

Explanation

Sugar is not a crystal because it does not have a regular repeating pattern of molecules or ions in its structure. Graphite, ice, and potassium chloride all have a crystalline structure, meaning their molecules or ions are arranged in a repeating pattern.

47. The pressure at the ice point for a constant-volume gas thermometer is 4.81 x 10⁴ Pa while that at the steam point is 6.48 x 10⁴ Pa. What pressure would this thermometer indicate at 50⁰C?

5.645 x 100C

7.230 x 100C

2.543 x 100C

9.471 x 100C

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

48. When the pointed end of an uncharged optical pin is brought near the cap of a positively charged electroscope, it is observed that the gold leaves

Collapse slowly

Vibrate

Are not affected

Diverge rapidly

When the pointed end of an uncharged optical pin is brought near the cap of a positively charged electroscope, the positive charges in the electroscope are attracted to the negative charges in the pin. This causes the positive charges in the electroscope to move closer to the pin, resulting in the collapse of the gold leaves. Since the pin is uncharged, there is no repulsion between the charges in the electroscope, which is why the collapse is slow rather than rapid.

Explanation

When the pointed end of an uncharged optical pin is brought near the cap of a positively charged electroscope, the positive charges in the electroscope are attracted to the negative charges in the pin. This causes the positive charges in the electroscope to move closer to the pin, resulting in the collapse of the gold leaves. Since the pin is uncharged, there is no repulsion between the charges in the electroscope, which is why the collapse is slow rather than rapid.

49. The readings on the pressure scale at the steam and ice points are 800mmHg and 300mmHg respectively. Determine the corresponding temperature in degree Celsius when it reads 450mmHg.

15

30

45

60

The correct answer is 30. The pressure and temperature of a substance are directly proportional, according to Gay-Lussac's Law. Therefore, we can use the proportionality to find the corresponding temperature. The difference between the pressure at the steam point and the ice point is 800mmHg - 300mmHg = 500mmHg. The difference between the temperature at the steam point and the ice point is 100°C. Therefore, the temperature corresponding to a pressure of 450mmHg can be calculated using the proportion: (450mmHg - 300mmHg) / 500mmHg = (T - 30°C) / 100°C. Solving for T gives T = 30°C.

Explanation

The correct answer is 30. The pressure and temperature of a substance are directly proportional, according to Gay-Lussac's Law. Therefore, we can use the proportionality to find the corresponding temperature. The difference between the pressure at the steam point and the ice point is 800mmHg - 300mmHg = 500mmHg. The difference between the temperature at the steam point and the ice point is 100°C. Therefore, the temperature corresponding to a pressure of 450mmHg can be calculated using the proportion: (450mmHg - 300mmHg) / 500mmHg = (T - 30°C) / 100°C. Solving for T gives T = 30°C.

50. The property considered when selecting a wire to be used as a fuse is its

Conductivity

Cross sectional area

Length

Melting point

The property considered when selecting a wire to be used as a fuse is its melting point. This is because a fuse is designed to melt and break the circuit when there is an excessive current flow, thus protecting the electrical system from damage. By choosing a wire with a specific melting point, the fuse can be calibrated to break at a desired current level.

Explanation

The property considered when selecting a wire to be used as a fuse is its melting point. This is because a fuse is designed to melt and break the circuit when there is an excessive current flow, thus protecting the electrical system from damage. By choosing a wire with a specific melting point, the fuse can be calibrated to break at a desired current level.

51. Which of the following cannot be explained by the molecular theory of matter?

Conduction

Convection

Expansion

Radiation

Conduction is the transfer of heat through direct contact between particles. The molecular theory of matter explains that heat is transferred through the collision of particles. However, conduction cannot be explained solely by this theory because it also involves the movement of free electrons in conductive materials. Therefore, the molecular theory of matter cannot fully explain conduction.

Explanation

Conduction is the transfer of heat through direct contact between particles. The molecular theory of matter explains that heat is transferred through the collision of particles. However, conduction cannot be explained solely by this theory because it also involves the movement of free electrons in conductive materials. Therefore, the molecular theory of matter cannot fully explain conduction.

52. A platinum-resistance thermometer has a resistance of 4ῼ at 0⁰C and 12ῼ at 100⁰C. Assuming that the resistance changes uniformly with temperature, calculate the resistance of the thermometer when the temperature is 45⁰C.

6.0 ῼ

6.4 ῼ

7.6 ῼ

8.4 ῼ

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

53. An object weighs 60.0N in air, 48.2N in a certain liquid X and 44.9N in water. Calculate the relative density of X.

3.300

1.279

0.932

0.782

The relative density of a substance is defined as the ratio of its density to the density of a reference substance. In this case, the reference substance is water.

To calculate the relative density of X, we need to find the density of X first.

The weight of the object in air is 60.0N. Weight is equal to the force of gravity acting on an object, which is equal to the mass of the object multiplied by the acceleration due to gravity.

So, we can calculate the mass of the object using the formula: mass = weight / acceleration due to gravity.

The acceleration due to gravity is approximately 9.8 m/s^2.

Therefore, mass = 60.0N / 9.8 m/s^2 = 6.12 kg.

Now, let's calculate the density of X. Density is defined as mass divided by volume.

The volume of the object can be calculated using the formula: volume = weight in air / density of air.

The density of air is very small compared to the density of liquids, so we can neglect it.

Therefore, volume = 60.0N / density of X.

Now, we can calculate the density of X using the formula: density = mass / volume.

density of X = 6.12 kg / (60.0N / density of X).

Simplifying the equation, we get: density of X = 6.12 kg * density of X / 60.0N.

Now, let's calculate the density of X by substituting the given weights in the equation.

For the weight in X, the mass is the same (6.12 kg), but the force of gravity acting on it is different (48.2N).

So, we get: density of X = 6.12 kg * density of X / 48.2N.

Similarly, for the weight in water, the mass is the same (6.12 kg), but the force of gravity acting on it is different (44.9N).

So, we get: density of X = 6.12 kg * density of X / 44.9N.

Comparing the two equations, we can see that the density of X is the same in both cases.

Therefore, we can equate the two equations to find the density of X.

6.12 kg *

Explanation

The relative density of a substance is defined as the ratio of its density to the density of a reference substance. In this case, the reference substance is water.

To calculate the relative density of X, we need to find the density of X first.

The weight of the object in air is 60.0N. Weight is equal to the force of gravity acting on an object, which is equal to the mass of the object multiplied by the acceleration due to gravity.

So, we can calculate the mass of the object using the formula: mass = weight / acceleration due to gravity.

The acceleration due to gravity is approximately 9.8 m/s^2.

Therefore, mass = 60.0N / 9.8 m/s^2 = 6.12 kg.

Now, let's calculate the density of X. Density is defined as mass divided by volume.

The volume of the object can be calculated using the formula: volume = weight in air / density of air.

The density of air is very small compared to the density of liquids, so we can neglect it.

Therefore, volume = 60.0N / density of X.

Now, we can calculate the density of X using the formula: density = mass / volume.

density of X = 6.12 kg / (60.0N / density of X).

Simplifying the equation, we get: density of X = 6.12 kg * density of X / 60.0N.

Now, let's calculate the density of X by substituting the given weights in the equation.

For the weight in X, the mass is the same (6.12 kg), but the force of gravity acting on it is different (48.2N).

So, we get: density of X = 6.12 kg * density of X / 48.2N.

Similarly, for the weight in water, the mass is the same (6.12 kg), but the force of gravity acting on it is different (44.9N).

So, we get: density of X = 6.12 kg * density of X / 44.9N.

Comparing the two equations, we can see that the density of X is the same in both cases.

Therefore, we can equate the two equations to find the density of X.

6.12 kg *

54. Which of the following factors does not affect the electrical resistance of a wire?

Length

Mass

Temperature

Cross-sectional area

*##*Correct*##*Wrong

Explanation

*##*Correct*##*Wrong

55. Alcohol of mass 21g and density 0.7gcm^-3 is mixed with 10g of water. Determine the density of the mixture. [Density of water = 1.0gcm^-3]

0.775 gcm-3

0.780 gcm-3

0.875 gcm-3

0.880 gcm-3

The density of a substance is calculated by dividing its mass by its volume. In this question, the mass of the alcohol is given as 21g and its density is given as 0.7g/cm3. To find the volume of the alcohol, we can use the formula density = mass/volume and rearrange it to volume = mass/density. Plugging in the values, we get volume = 21g/0.7g/cm3 = 30cm3. The mass of water is given as 10g and its density is given as 1.0g/cm3, so its volume is 10cm3. To find the density of the mixture, we add the volumes of alcohol and water and divide the total mass (31g) by the total volume (40cm3). This gives us a density of 0.775g/cm3.

Explanation

The density of a substance is calculated by dividing its mass by its volume. In this question, the mass of the alcohol is given as 21g and its density is given as 0.7g/cm3. To find the volume of the alcohol, we can use the formula density = mass/volume and rearrange it to volume = mass/density. Plugging in the values, we get volume = 21g/0.7g/cm3 = 30cm3. The mass of water is given as 10g and its density is given as 1.0g/cm3, so its volume is 10cm3. To find the density of the mixture, we add the volumes of alcohol and water and divide the total mass (31g) by the total volume (40cm3). This gives us a density of 0.775g/cm3.

56. A battery of emf 12.0v and internal resistance 0.5ῼ is connected to 1.5ῼ and 4.0ῼ series resistors. Calculate the terminal voltage of the battery.

13.0V

11.0V

3.0V

1.0V

The terminal voltage of a battery can be calculated using the formula V = E - Ir, where V is the terminal voltage, E is the emf of the battery, I is the current flowing through the circuit, and r is the internal resistance of the battery. In this case, the emf of the battery is 12.0V and the internal resistance is 0.5Ω. The total resistance in the circuit is 1.5Ω + 4.0Ω = 5.5Ω. Using Ohm's law, we can calculate the current flowing through the circuit as I = V/R = 12.0V / 5.5Ω = 2.18A. Substituting the values into the formula, we get V = 12.0V - (2.18A * 0.5Ω) = 13.0V. Therefore, the terminal voltage of the battery is 13.0V.

Explanation

The terminal voltage of a battery can be calculated using the formula V = E - Ir, where V is the terminal voltage, E is the emf of the battery, I is the current flowing through the circuit, and r is the internal resistance of the battery. In this case, the emf of the battery is 12.0V and the internal resistance is 0.5Ω. The total resistance in the circuit is 1.5Ω + 4.0Ω = 5.5Ω. Using Ohm's law, we can calculate the current flowing through the circuit as I = V/R = 12.0V / 5.5Ω = 2.18A. Substituting the values into the formula, we get V = 12.0V - (2.18A * 0.5Ω) = 13.0V. Therefore, the terminal voltage of the battery is 13.0V.

57. A faulty thermometer registers 102.5⁰C at 100⁰C. If the thermometer has no zero error, what will it register at 55⁰C ?

54.6 oC

55.0 oC

56.0 oC

56.4 oC

The faulty thermometer registers a temperature that is 2.5 degrees higher than the actual temperature. Therefore, if the actual temperature is 55 degrees Celsius, the thermometer will register 55 + 2.5 = 57.5 degrees Celsius. However, since the thermometer has no zero error, we need to subtract the error at 0 degrees Celsius. Since the error is 2.5 degrees at 100 degrees Celsius, it will be 2.5 * (55/100) = 1.375 degrees at 55 degrees Celsius. Therefore, the thermometer will register 57.5 - 1.375 = 56.125 degrees Celsius, which is closest to 56.4 degrees Celsius.

Explanation

The faulty thermometer registers a temperature that is 2.5 degrees higher than the actual temperature. Therefore, if the actual temperature is 55 degrees Celsius, the thermometer will register 55 + 2.5 = 57.5 degrees Celsius. However, since the thermometer has no zero error, we need to subtract the error at 0 degrees Celsius. Since the error is 2.5 degrees at 100 degrees Celsius, it will be 2.5 * (55/100) = 1.375 degrees at 55 degrees Celsius. Therefore, the thermometer will register 57.5 - 1.375 = 56.125 degrees Celsius, which is closest to 56.4 degrees Celsius.

58. The magnitude of an expansion or contraction of a substance depends on the I. temperature change II. Nature of the substance III. Size of the substance

I and II only

II and III only

I and III only

I, II and III

The magnitude of an expansion or contraction of a substance depends on the temperature change, the nature of the substance, and the size of the substance. This means that all three factors play a role in determining the extent of expansion or contraction. Temperature change affects the kinetic energy of the particles, causing them to move faster or slower, leading to expansion or contraction. The nature of the substance determines its molecular structure and bonding, which affects its ability to expand or contract. The size of the substance determines the amount of material present, which can also impact the magnitude of expansion or contraction.

Explanation

The magnitude of an expansion or contraction of a substance depends on the temperature change, the nature of the substance, and the size of the substance. This means that all three factors play a role in determining the extent of expansion or contraction. Temperature change affects the kinetic energy of the particles, causing them to move faster or slower, leading to expansion or contraction. The nature of the substance determines its molecular structure and bonding, which affects its ability to expand or contract. The size of the substance determines the amount of material present, which can also impact the magnitude of expansion or contraction.

59. A rod 150cm long and of diameter 2cm is subjected to an axial pull of 20kN. What will be the stress?

60 N/mm2

65 N/mm2

63.6 N/mm2

71.2 N/mm2

*##*Correct*##*Wrong

Explanation

*##*Correct*##*Wrong

60. A negatively charged rod is held close to an uncharged metal ball on an insulating stand. The ball will

Be negatively charged

Be positively charged

Have an excess of negative charges on the side nearest the rod

Have an excess of positive charges on the side nearest the rod

When a negatively charged rod is held close to an uncharged metal ball, the negatively charged rod repels the electrons in the metal ball. As a result, the electrons are pushed away from the rod and towards the opposite side of the ball. This causes an excess of positive charges to accumulate on the side of the ball nearest to the rod, while the side farthest from the rod remains neutral. Therefore, the correct answer is "have an excess of positive charges on the side nearest the rod."

Explanation

When a negatively charged rod is held close to an uncharged metal ball, the negatively charged rod repels the electrons in the metal ball. As a result, the electrons are pushed away from the rod and towards the opposite side of the ball. This causes an excess of positive charges to accumulate on the side of the ball nearest to the rod, while the side farthest from the rod remains neutral. Therefore, the correct answer is "have an excess of positive charges on the side nearest the rod."

61. Density is a measure of the

Quantity of matter an object contains

Space an object occupies

Compactness of matter with respect to its size

Surface area of an object

Density is a measure of the compactness of matter with respect to its size. It represents how much mass is packed into a given volume of an object. Objects with higher density have more matter packed into a smaller space, while objects with lower density have less matter spread out over a larger space. Therefore, the correct answer is "compactness of matter with respect to its size."

Explanation

Density is a measure of the compactness of matter with respect to its size. It represents how much mass is packed into a given volume of an object. Objects with higher density have more matter packed into a smaller space, while objects with lower density have less matter spread out over a larger space. Therefore, the correct answer is "compactness of matter with respect to its size."

62. In which of the following states of matter do the molecules vibrate about their mean positions?

Liquids only

Solids only

Liquids and gases only

Solids, liquids and gases

Solids only have molecules that vibrate about their mean positions. In solids, the molecules are tightly packed and have strong intermolecular forces that hold them in fixed positions, but they still vibrate due to thermal energy. In liquids and gases, the molecules are not held in fixed positions and are more free to move and flow, so they do not vibrate about their mean positions like in solids.

Explanation

Solids only have molecules that vibrate about their mean positions. In solids, the molecules are tightly packed and have strong intermolecular forces that hold them in fixed positions, but they still vibrate due to thermal energy. In liquids and gases, the molecules are not held in fixed positions and are more free to move and flow, so they do not vibrate about their mean positions like in solids.

63. The limit beyond which the material does not behave elastically is known as

Proportional limit

Elastic limit

Plastic limit

Yield point

*##*correct*##*wrong

Explanation

*##*correct*##*wrong

64. The opposing capacity of materials against the current flow is

Resistance

Inductance

Susceptance

Conductance

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

65. Which of the following statement is not correct

Like charges attract

Like charges repel

Unlike charges attract then repel

Unlike charges repel and then attract

Like charges repel because they have the same charge, either positive or negative. According to the principle of electrostatics, like charges will exert a force on each other that pushes them away. This is due to the electrostatic force, which is the force between two charged objects. When the charges are the same, the force is repulsive, causing the charges to repel each other. This phenomenon is observed in various situations, such as when two positively charged objects or two negatively charged objects are brought close to each other.

Explanation

Like charges repel because they have the same charge, either positive or negative. According to the principle of electrostatics, like charges will exert a force on each other that pushes them away. This is due to the electrostatic force, which is the force between two charged objects. When the charges are the same, the force is repulsive, causing the charges to repel each other. This phenomenon is observed in various situations, such as when two positively charged objects or two negatively charged objects are brought close to each other.

66. A cube of sides 2.5cm is completely immersed in a liquid of relative density 0.75, calculate the mass of the liquid displaced [Density of water = 1.0gcm³]

11.72 g

18.75 g

20.85 g

30.00 g

When a cube is completely immersed in a liquid, it displaces a volume of liquid equal to its own volume. The volume of the cube can be calculated by finding the volume of a cube using the formula V = s^3, where s is the length of the side of the cube. In this case, the side length is 2.5 cm, so the volume of the cube is 2.5^3 = 15.625 cm^3.

The mass of the liquid displaced can be found by multiplying the volume of the liquid displaced by the density of the liquid. The density of the liquid is given as 0.75 times the density of water, which is 1.0 g/cm^3. Therefore, the mass of the liquid displaced is 15.625 cm^3 * 0.75 g/cm^3 = 11.72 g.

Explanation

When a cube is completely immersed in a liquid, it displaces a volume of liquid equal to its own volume. The volume of the cube can be calculated by finding the volume of a cube using the formula V = s^3, where s is the length of the side of the cube. In this case, the side length is 2.5 cm, so the volume of the cube is 2.5^3 = 15.625 cm^3.

The mass of the liquid displaced can be found by multiplying the volume of the liquid displaced by the density of the liquid. The density of the liquid is given as 0.75 times the density of water, which is 1.0 g/cm^3. Therefore, the mass of the liquid displaced is 15.625 cm^3 * 0.75 g/cm^3 = 11.72 g.

67. An electrician wishes to cut a copper wire (ρ=1.724∗10−8Ωm) that has no more than 10Ω of resistance. The wire has a radius of 0.725mm. Approximately what length of wire has a resistance equal to the maximum 10Ω ?

960 M

478 M

356 M

200 M

*##*Correct*##*Incorrect

Explanation

*##*Correct*##*Incorrect

68. When brass of length 100cm at 50cm is heated, its length changes to 100.054cm at ___. [Linear expansivity of brass = 0.000018k^-1]

510C

540C

720C

800C

When brass is heated, it undergoes thermal expansion, causing its length to increase. The linear expansivity of brass is given as 0.000018k-1. This means that for every degree Celsius increase in temperature, the length of brass increases by 0.000018 times its original length. In this case, the initial length of the brass is 100cm and it changes to 100.054cm when heated. To find the temperature at which this occurs, we can set up the equation: (change in length) = (linear expansivity) * (initial length) * (change in temperature). Plugging in the given values, we get (100.054 - 100) = 0.000018 * 100 * (change in temperature). Solving for the change in temperature, we find that it is approximately 800C. Therefore, the correct answer is 800C.

Explanation

When brass is heated, it undergoes thermal expansion, causing its length to increase. The linear expansivity of brass is given as 0.000018k-1. This means that for every degree Celsius increase in temperature, the length of brass increases by 0.000018 times its original length. In this case, the initial length of the brass is 100cm and it changes to 100.054cm when heated. To find the temperature at which this occurs, we can set up the equation: (change in length) = (linear expansivity) * (initial length) * (change in temperature). Plugging in the given values, we get (100.054 - 100) = 0.000018 * 100 * (change in temperature). Solving for the change in temperature, we find that it is approximately 800C. Therefore, the correct answer is 800C.

69. When a resistor or resistance R is connected across a cell, the terminal p.d of the cell is reduced to three quarters of its emf. The cells internal resistance in terms of R is

R/4

R/3

R/2

2R/3

When a resistor or resistance R is connected across a cell, it creates a voltage drop across the resistor. This voltage drop reduces the terminal potential difference (p.d) of the cell. In this case, the terminal p.d is reduced to three quarters of its electromotive force (emf). This means that the voltage drop across the internal resistance of the cell is equal to one quarter of the emf. Since the internal resistance is in series with the resistor R, the voltage drop across it is also equal to one quarter of the emf. Therefore, the internal resistance in terms of R is R/4.

Explanation

When a resistor or resistance R is connected across a cell, it creates a voltage drop across the resistor. This voltage drop reduces the terminal potential difference (p.d) of the cell. In this case, the terminal p.d is reduced to three quarters of its electromotive force (emf). This means that the voltage drop across the internal resistance of the cell is equal to one quarter of the emf. Since the internal resistance is in series with the resistor R, the voltage drop across it is also equal to one quarter of the emf. Therefore, the internal resistance in terms of R is R/4.