1.
If a copper wire is stretched to double of its length, then the value of resistance becomes
Correct Answer
B. 4 times
Explanation
When a copper wire is stretched to double its length, its resistance increases by a factor of 4. This is because resistance is directly proportional to the length of the wire. When the length is doubled, the resistance also doubles, resulting in a 4 times increase in resistance.
2.
Magnetic field lines are always
Correct Answer
D. Closed loops
Explanation
Magnetic field lines are always closed loops because they represent the continuous path that a magnetic field takes around a magnet or a current-carrying wire. The lines form closed loops because a magnetic field is a continuous and unbroken flow of magnetic force. This is consistent with the observation that magnetic field lines always form closed loops when visualized using iron filings or a magnetic compass. The closed loops indicate that the magnetic field is continuous and does not have any starting or ending points.
3.
Lenz’s law is a consequence of the law of conservation of
Correct Answer
D. Energy
Explanation
Lenz's law is a consequence of the law of conservation of energy. It states that when a change in magnetic field occurs, an induced current is generated in such a way that it opposes the change that produced it. This is because the induced current creates a magnetic field that opposes the original change. This conservation of energy is evident in Lenz's law as the induced current works to counteract the change in magnetic field, thereby conserving the energy in the system.
4.
Image formed by plane mirror
Correct Answer
C. May be real or virtual
Explanation
The image formed by a plane mirror can be either real or virtual. A real image is formed when the reflected rays actually converge at a point, while a virtual image is formed when the rays only appear to converge when extended backward. In the case of a plane mirror, the image formed is virtual, as the rays of light do not actually converge but appear to diverge from behind the mirror. However, it is important to note that the image appears to be behind the mirror and is not physically present. Therefore, the correct answer is "May be real or virtual."
5.
An ion X2- contains 10 electrons and 8 neutrons. What are the atomic number and mass number of element X?
Correct Answer
B. 8, 16
Explanation
The atomic number of an element corresponds to the number of protons in its nucleus. Since the ion X2- contains 10 electrons, it means that there are 10 more electrons than protons. Therefore, the atomic number of element X is 10. The mass number of an element is the sum of its protons and neutrons. Given that the ion X2- contains 8 neutrons, the mass number of element X is 10 (protons) + 8 (neutrons) = 18.
6.
The pH of carbonated drink is
Correct Answer
A.
7.
Which of the following statements is correct about the given reaction? AB + C ----> CB +A
Correct Answer
B. C is more reactive than A
Explanation
The correct answer is "C is more reactive than A." This means that C is more likely to undergo a chemical reaction compared to A. Reactivity is a property that describes how easily a substance can undergo a chemical reaction. In this reaction, C is being transformed into CB, indicating that it is more reactive than A, which remains unchanged.
8.
During electrolysis of water , the reaction involved is 2H2O (l) -----> 2H2(g) + O2(g)The charges carried by anode and cathode respectively is
Correct Answer
C. +,-
Explanation
During electrolysis of water, the reaction involves the decomposition of water into hydrogen gas and oxygen gas. This reaction occurs through the flow of electric current. At the anode, which is the positive electrode, water molecules lose electrons and form oxygen gas. Therefore, the anode carries a positive charge. At the cathode, which is the negative electrode, water molecules gain electrons and form hydrogen gas. Therefore, the cathode carries a negative charge. Hence, the charges carried by the anode and cathode respectively are + and -.
9.
In 2.495 gm of CuSO4.5H2O (Molar Mass= 249.5) , total number of atoms present are
(1 NA = 6.022*1023)
Correct Answer
B. 0.21 NA
Explanation
In 2.495 gm of CuSO4.5H2O, there are 5 water molecules (H2O), each containing 3 atoms (2 hydrogen and 1 oxygen). Therefore, there are a total of 5 x 3 = 15 atoms from water. Additionally, there is 1 copper atom (Cu), 1 sulfur atom (S), and 4 oxygen atoms (O) in CuSO4. So, the total number of atoms present is 15 + 1 + 1 + 4 = 21 atoms. Since 1 mole of any substance contains 6.022 x 10^23 atoms, 21 atoms is equivalent to 21/6.022 x 10^23 = 0.348 moles. And since 1 mole is equal to Avogadro's number (NA), the total number of atoms present is 0.348 NA, which is closest to 0.21 NA.
10.
The value of tan85× tan80 × tan75 × … × tan5 is
Correct Answer
C. 1
Explanation
The value of the product of tangent of angles from 5 degrees to 85 degrees can be simplified using the identity tan(A+B) = (tanA + tanB) / (1 - tanA tanB). By applying this identity repeatedly, we can simplify the expression to tan45, which equals 1. Therefore, the correct answer is 1.
11.
If the positive square root of 4 is 2 then the positive square root of 0.4 (upto one place of decimal) is
Correct Answer
C. 0.6
Explanation
The positive square root of a number is the value that, when multiplied by itself, gives the original number. In this case, the positive square root of 4 is 2 because 2 multiplied by 2 equals 4. Therefore, if the positive square root of 4 is 2, then the positive square root of 0.4 would be a value greater than 0.2 and less than 0.3. The only option that fits this criteria is 0.2, so the correct answer is 0.2.
12.
There are deer and peacocks in a zoo. By counting heads they are 80. The number of their legs is 200. The number of peacocks in the zoo are
Correct Answer
D. 60
Explanation
If we let x represent the number of deer and y represent the number of peacocks, we can set up a system of equations. From the information given, we know that x + y = 80 (since the total number of deer and peacocks is 80) and 4x + 2y = 200 (since each deer has 4 legs and each peacock has 2 legs). Solving this system of equations, we find that x = 20 and y = 60. Therefore, the number of peacocks in the zoo is 60.
13.
A woman says, “If you reverse my own age, the figure represent my husband’s age. He is of course, senior to me and the difference between our ages is one - eleventh of their sum.” The woman’s age is
Correct Answer
C. 45
Explanation
The woman's age can be determined by using the information given in the statement. If we reverse her age (54), it represents her husband's age. Since her husband is senior to her, her age must be less than 54. Additionally, the difference between their ages is one-eleventh of their sum. This means that the husband's age minus the woman's age is equal to one-eleventh of their sum. By solving this equation, we can find that the woman's age is 45.
14.
If 5 √3 is multiplied with √27 , we get
Correct Answer
B. 45
Explanation
When we multiply 5 √3 with √27, we can simplify it by multiplying the numbers outside the square roots (5 and 27) and the numbers inside the square roots (√3 and √27). Multiplying 5 and 27 gives us 135. Then, multiplying √3 and √27 gives us √(3 * 27) = √81 = 9. Therefore, the result of multiplying 5 √3 with √27 is 135 * 9 = 1215. However, none of the given options match this result, so the correct answer is not available.
15.
In a right ∆ ABC in which angle ABC = 90, AB = 1 cm and AC = 2 cm. The measure of angle ACB is
Correct Answer
A. 30 degrees
Explanation
In a right triangle ABC, the right angle is at B. The length of side AB is given as 1 cm and the length of side AC is given as 2 cm. In a right triangle, the angles are always complementary, meaning they add up to 90 degrees. Since angle ABC is 90 degrees, the sum of angles BAC and ACB must also be 90 degrees. Therefore, angle ACB must be 90 - 60 = 30 degrees.
16.
Which of the following points lie on the graph of the equation 3x – 4y = 10?
Correct Answer
D. (2, –1)
Explanation
The equation 3x - 4y = 10 can be solved by substituting the x and y values of each point into the equation. When we substitute x = 2 and y = -1 into the equation, we get 3(2) - 4(-1) = 6 + 4 = 10. Since the equation is satisfied by the point (2, -1), it lies on the graph of the equation.
17.
The difference between 20th term and 12th term of the AP : 2, 13, 24, 35, ... is
Correct Answer
B. 88
Explanation
The given arithmetic progression (AP) has a common difference of 11. To find the difference between the 20th and 12th terms, we can subtract the 12th term from the 20th term. The 12th term can be found by adding 11 to the first term (2) twelve times. This gives us 2 + 11*12 = 2 + 132 = 134. The 20th term can be found by adding 11 to the first term (2) nineteen times. This gives us 2 + 11*19 = 2 + 209 = 211. Finally, subtracting the 12th term (134) from the 20th term (211) gives us 211 - 134 = 77. Therefore, the correct answer is 77.
18.
The sum of first 10 terms of the AP given below is –7, –11, –15, ...
Correct Answer
C. -250
Explanation
The given arithmetic progression (AP) has a common difference of -4. To find the sum of the first 10 terms, we can use the formula for the sum of an AP: Sn = (n/2)(2a + (n-1)d), where Sn is the sum of the first n terms, a is the first term, and d is the common difference. Plugging in the values, we get Sn = (10/2)(2*(-7) + (10-1)*(-4)) = 5*(-14 - 36) = 5*(-50) = -250. Therefore, the correct answer is -250.
19.
Which of the following points lie on the graph of the equation 3x – 4y = 10?
Correct Answer
D. (2, –1)
Explanation
The equation 3x - 4y = 10 represents a straight line on a coordinate plane. To determine which points lie on this line, we can substitute the x and y values of each point into the equation and see if the equation holds true. By substituting x = 2 and y = -1 into the equation, we get 3(2) - 4(-1) = 6 + 4 = 10, which satisfies the equation. Therefore, the point (2, -1) lies on the graph of the equation 3x - 4y = 10.
20.
The length of an arc of a circle of radius 14 cm and having central angle as 45 degree is
Correct Answer
A. 11 cm
Explanation
The length of an arc of a circle can be calculated using the formula L = (θ/360) * 2πr, where L is the length of the arc, θ is the central angle in degrees, and r is the radius of the circle. In this case, the radius is given as 14 cm and the central angle is 45 degrees. Plugging these values into the formula, we get L = (45/360) * 2π(14) = (1/8) * 2π(14) = π cm ≈ 11 cm. Therefore, the correct answer is 11 cm.
21.
Which of the following constructions of a triangle is not possible?
Correct Answer
C. Perimeter of the triangle and its one base
angle are given
Explanation
The perimeter of a triangle is the sum of the lengths of all three sides. However, knowing only the perimeter and one base angle of a triangle does not provide enough information to determine the lengths of the individual sides. Therefore, it is not possible to construct a triangle with only the perimeter and one base angle given.
22.
If the area of a triangle having (3, 2), (x, –4) and (5, 0) as coordinates of its vertices is 9 sq. units, then the value of x is
Explanation
To find the value of x, we can use the formula for the area of a triangle given its coordinates. We know that the area is 9 sq. units. Using the formula, we can substitute the coordinates into the formula and solve for x. The formula for the area of a triangle with vertices (x1, y1), (x2, y2), and (x3, y3) is (1/2) * |x1(y2 - y3) + x2(y3 - y1) + x3(y1 - y2)|. Plugging in the coordinates, we get (1/2) * |3(-4 - 0) + x(0 - 2) + 5(2 - (-4))| = 9. Simplifying the equation, we get |12 - 2x + 30| = 18. Solving for x, we get x = 1. Therefore, the value of x is 1.
23.
If area of sector of a circle of radius 14 cm is
77 cm sq, then the central angle of the sector is
Correct Answer
C. 45 degrees
Explanation
The area of a sector is given by the formula A = (θ/360)πr², where A is the area, θ is the central angle, and r is the radius. In this case, we are given that the area is 77 cm² and the radius is 14 cm. Plugging these values into the formula, we get 77 = (θ/360)π(14)². Solving for θ, we find that θ ≈ 45 degrees. Therefore, the central angle of the sector is 45 degrees.
24.
The inability to see the nearby objects distinctly and comfortably, might be a symptom for
Correct Answer
C. Hypermetropia or presbyopia
Explanation
The inability to see nearby objects distinctly and comfortably can be a symptom of hypermetropia or presbyopia. Hypermetropia, also known as farsightedness, occurs when the eye is unable to focus on close objects due to the shape of the eye or the cornea being too flat. Presbyopia, on the other hand, is an age-related condition where the lens of the eye loses its flexibility, making it difficult to focus on nearby objects. Both conditions can result in blurred vision when looking at objects up close. Cataract, which is the clouding of the lens, and myopia, or nearsightedness, do not typically cause difficulty in seeing nearby objects.
25.
If a concave mirror forms an enlarged image of a real object placed on principal axis, then the image
Correct Answer
B. Can be either real or erect, not both
Explanation
If a concave mirror forms an enlarged image of a real object placed on the principal axis, the image can be either real or erect, but not both. A real image is formed when the light rays actually converge at a point, and it can be projected onto a screen. An erect image is one that is not inverted, meaning it appears in the same orientation as the object. In this case, the image can be either real (if the light rays converge) or erect (if the image is not inverted), but it cannot be both at the same time.
26.
In dispersion of light by a glass prism, the light having smallest angle of deviation among the following is
Correct Answer
D. Orange light
Explanation
The light having the smallest angle of deviation in dispersion of light by a glass prism is orange light.
27.
The colour of the scattered light in Tyndal effect mainly depends on
Correct Answer
B. Size of the scattering particles
Explanation
The Tyndall effect refers to the scattering of light by particles in a medium. The size of the scattering particles is the main factor that determines the color of the scattered light. When the size of the particles is comparable to the wavelength of light, shorter wavelengths (such as blue and violet) are scattered more effectively than longer wavelengths (such as red and orange). This is why the sky appears blue during the day, as the smaller particles in the atmosphere scatter the shorter blue wavelengths more than the longer red wavelengths. Therefore, the size of the scattering particles is the primary factor affecting the color of the scattered light in the Tyndall effect.
28.
Identify the incorrect statement.
Correct Answer
B. A strong metal with low melting point is used
for making bulb filaments
Explanation
The incorrect statement is "A strong metal with low melting point is used for making bulb filaments." In reality, the filament of a bulb is usually made up of tungsten, which is a strong metal with a high melting point. This is because tungsten has a high melting point, allowing it to withstand the high temperatures generated by the electric current passing through it, and it is also strong enough to maintain its shape and structure under these conditions.
29.
Gobar-gas is another name for
Correct Answer
B. Biogas
Explanation
Gobar-gas is another name for biogas. Biogas is a type of gas that is produced through the anaerobic digestion of organic matter, such as cow dung or slurry. It is composed mainly of methane, along with small amounts of carbon dioxide and other gases. Gobar-gas is commonly used as a source of renewable energy for cooking, heating, and electricity generation.
30.
PH of milk of magnesia is
Correct Answer
C. More than 7
Explanation
Milk of magnesia is an alkaline solution of magnesium hydroxide. When dissolved in water, it releases hydroxide ions (OH-) which makes the solution basic. A pH value greater than 7 indicates alkalinity, so the correct answer is "More than 7".
31.
Which of the given elements has the least atomic radii?
Correct Answer
B. Li
Explanation
Li has the least atomic radii among the given elements. Atomic radii generally increase as you move down a group in the periodic table. Since Na, Cs, and Rb are all located below Li in the same group (Group 1), their atomic radii would be larger than that of Li. Therefore, Li has the smallest atomic radii among these elements.
32.
In some countries alcohol is used as an additive in petrol because
Correct Answer
C. It is a cleaner fuel
Explanation
Alcohol is used as an additive in petrol because it is a cleaner fuel. Adding alcohol to petrol helps to reduce emissions and improve the overall combustion efficiency of the fuel. This is because alcohol has a higher oxygen content compared to petrol, which leads to more complete combustion and fewer harmful pollutants being released into the environment. Additionally, alcohol has a lower carbon content, making it a cleaner alternative to traditional petrol.
33.
Cinnabar is an ore of
Correct Answer
B. Mercury
Explanation
Cinnabar is an ore of mercury. Cinnabar is a bright red mineral that is the main source of mercury. It is commonly found in volcanic regions and is used in various applications such as pigments, cosmetics, and traditional medicine. Mercury is extracted from cinnabar through a process called roasting, where the mineral is heated to release the mercury vapor, which is then condensed and purified.
34.
An atom has 7 electrons in its M-shell, the atomic number of that atom is
Correct Answer
D. 7
Explanation
The atom has 7 electrons in its M-shell, which means that the M-shell is fully filled. In an atom, the atomic number represents the number of protons in the nucleus. Since the M-shell is fully filled, it indicates that there are 7 protons in the nucleus, which is the atomic number of the atom. Therefore, the correct answer is 7.
35.
The main cause of tidal energy is
Correct Answer
D. Gravitational pull of Moon
Explanation
Tidal energy is primarily caused by the gravitational pull of the Moon. The Moon's gravitational force creates a tidal bulge on the Earth's oceans, causing them to rise and fall in a regular pattern. As the Earth rotates on its axis, different parts of the ocean experience high and low tides. This tidal movement can be harnessed to generate electricity through various technologies, such as tidal turbines. While earthquakes and volcanoes near the ocean can have some impact on tidal patterns, they are not the main cause of tidal energy.
36.
A magnetic compass kept above a current carrying wire deflects towards west direction. The current in the wire is flowing from
Correct Answer
A. North to South
Explanation
A magnetic compass aligns itself with the Earth's magnetic field, which points from the geographic North Pole to the geographic South Pole. When a current flows through a wire, it creates a magnetic field around the wire. This magnetic field interacts with the Earth's magnetic field, causing the compass needle to deflect. According to the right-hand rule, the magnetic field around the wire is in the direction of the fingers when the thumb points in the direction of the current. Therefore, the current in the wire must be flowing from North to South for the compass to deflect towards the west direction.
37.
Select the group of biodegradable substances from the following.
Correct Answer
B. Wood, leather, paper and fruit
Explanation
The group of biodegradable substances consists of materials that can be broken down naturally by microorganisms and decompose over time. Wood, leather, paper, and fruit are examples of biodegradable substances because they are organic materials that can be broken down by bacteria, fungi, and other natural processes.