1.
Which of the following statements does not represent ohm's law?
Correct Answer
D. Current = resistance x potential difference
Explanation
This statement does not represent Ohm's law because according to Ohm's law, the potential difference (voltage) across a conductor is directly proportional to the current flowing through it, and inversely proportional to the resistance of the conductor. The correct representation of Ohm's law is given by the statement: potential difference = current x resistance.
2.
The unit of current is _____________.
Correct Answer
A. Ampere
Explanation
The unit of current is ampere. Ampere is the SI unit of electric current and is defined as one coulomb of charge passing through a conductor in one second. It is named after the French physicist AndrÃ©-Marie AmpÃ¨re, who made significant contributions to the study of electromagnetism.
3.
The potential difference required to pass a current 0.2 A in a wire of resistance 20W is ____.
Correct Answer
B. 4 V
Explanation
The potential difference required to pass a current of 0.2 A in a wire of resistance 20Î© can be calculated using Ohm's Law, which states that V = I * R. Plugging in the given values, we get V = 0.2 A * 20Î© = 4 V. Therefore, the correct answer is 4 V.
4.
The resistance of an electric bulb drawing 1.2 A current at 6.0 V is ___________.
Correct Answer
B. 5 ohms
Explanation
The resistance of an electric bulb can be calculated using Ohm's Law, which states that resistance (R) is equal to voltage (V) divided by current (I). In this case, the bulb is drawing a current of 1.2 A at a voltage of 6.0 V. Therefore, the resistance can be calculated as 6.0 V divided by 1.2 A, which equals 5 ohms.
5.
In the figure,
Correct Answer
D. 3 ohms , 6 ohms are in parallel and 9 W is in series
Explanation
The given answer suggests that the 3 ohms and 6 ohms resistors are connected in parallel, meaning that they share the same voltage across them. Additionally, the 9 ohms resistor is connected in series with the parallel combination. This means that the current flowing through the 9 ohms resistor is the same as the current flowing through the parallel combination of 3 ohms and 6 ohms. Therefore, the answer correctly identifies the arrangement of resistors in the circuit.
6.
When a current 'I' flows through a resistance 'R' for time 't' the electrical energy spent is given by ___________.
Correct Answer
B. I2 R t
Explanation
The electrical energy spent when a current 'I' flows through a resistance 'R' for time 't' is given by the formula I2 R t.
7.
When a fuse is rated 8 A, it means
Correct Answer
D. It will melt if current exceeds 8 A
Explanation
When a fuse is rated 8 A, it means it will melt if the current exceeds 8 A. A fuse is a safety device that is designed to protect electrical circuits from overcurrent. It contains a metal wire that melts when the current flowing through it exceeds its rated value. This melting of the wire breaks the circuit and prevents further damage to the electrical system. Therefore, if the current exceeds 8 A, the fuse will melt and interrupt the circuit, protecting the circuit from potential damage or fire hazards.
8.
The device used for measuring potential difference is known as _____________.
Correct Answer
D. Voltmeter
Explanation
A voltmeter is used to measure potential difference, also known as voltage. It is specifically designed to measure the voltage across a circuit or component. A potentiometer is a different device used to measure the potential difference, but it is not the correct answer in this case. An ammeter is used to measure electric current, while a galvanometer is used to detect and measure small electric currents. Therefore, the correct answer is voltmeter.
9.
The work done in moving a unit positive charge across two points in an electric circuit is a measure of ___________.
Correct Answer
B. Potential difference
Explanation
The work done in moving a unit positive charge across two points in an electric circuit is a measure of potential difference. Potential difference, also known as voltage, is the measure of the electric potential energy per unit charge. It represents the difference in electric potential between two points in the circuit and determines the direction and flow of electric current. The greater the potential difference, the more work is done in moving the charge and the higher the voltage in the circuit.
10.
The free electrons of a metal _____________.
Correct Answer
D. Are free to move anywhere in the metal
Explanation
The correct answer is that the free electrons of a metal are free to move anywhere in the metal. Metals have a unique structure where the outermost electrons of the atoms are not tightly bound to their respective nuclei. Instead, they form a "sea" of delocalized electrons that are free to move throughout the metal lattice. This mobility of electrons allows metals to conduct electricity and heat effectively.
11.
The current in a wire ______________.
Correct Answer
C. Depends on both resistance and potential difference
Explanation
The current in a wire depends on both the resistance and potential difference. The resistance of the wire determines how much the wire opposes the flow of current, while the potential difference applied determines the force that drives the flow of current. Therefore, both factors are necessary to determine the amount of current flowing through the wire.
12.
When there is an electric current passing through a wire, the particles moving are _____________.
Correct Answer
A. Electrons
Explanation
When there is an electric current passing through a wire, the particles that are moving are electrons. Electrons are negatively charged particles that carry the electrical charge in a circuit. They flow from the negative terminal of the power source to the positive terminal, creating the flow of electric current. Protons, atoms, and ions are not typically involved in the movement of electric current in a wire.
13.
A battery is used to ________________.
Correct Answer
A. Maintain a potential difference
Explanation
A battery is used to maintain a potential difference. When a battery is connected to a circuit, it creates a potential difference between its positive and negative terminals. This potential difference allows the flow of electric charges, creating an electric current in the circuit. The battery continuously supplies the necessary energy to maintain this potential difference, enabling the circuit to function properly. Without the battery, the potential difference would decrease, and the circuit would not be able to operate.
14.
Ohm's law relates potential difference with ___________.
Correct Answer
C. Current
Explanation
Ohm's law relates potential difference with current. According to Ohm's law, the current flowing through a conductor is directly proportional to the potential difference applied across it. This means that as the potential difference increases, the current also increases, and vice versa. Therefore, current is the correct answer as it is the quantity that is directly related to potential difference in Ohm's law.
15.
A solution of water and salt contains 35 grams of salt in 500 ml of water. What is the density of the salt water?
Correct Answer
A. 1.07 g/ml
Explanation
The density of a substance is defined as its mass per unit volume. In this case, the mass of the salt water is given as 35 grams, and the volume is given as 500 ml. To find the density, we divide the mass by the volume: 35 g / 500 ml = 0.07 g/ml. However, the answer is given as 1.07 g/ml, which suggests that there may be a typographical error in the question or answer choices. Without further information, it is difficult to determine the correct density.
16.
What is the density of the wooden log if it is 30cm long, has a cross sectional area of 10cm2 and weighs 200g
Correct Answer
C. 0.42 g/cm2
Explanation
The density of an object is calculated by dividing its mass by its volume. In this case, the mass of the wooden log is given as 200g. To find the volume, we need to multiply the cross-sectional area (10cm^2) by the length (30cm). The volume is therefore 10cm^2 * 30cm = 300cm^3. Dividing the mass by the volume gives us 200g / 300cm^3 = 0.67 g/cm^3. Therefore, the correct answer is 0.67 g/cm^3.
17.
Find the mass of 250.0 ml of benzone . The density of benzone is 0.8786 g/ml
Correct Answer
C. 219.6 g
Explanation
Given that the density of benzone is 0.8786 g/ml, we can use the formula mass = density x volume.
Since the volume is given as 250.0 ml, we can substitute these values into the formula to find the mass.
Mass = 0.8786 g/ml x 250.0 ml = 219.65 g.
Rounding to the nearest tenth, the mass of 250.0 ml of benzone is 219.6 g.
18.
A liquid has a mass density of 1550 kg/m2 . Calculate the specific gravity.
Correct Answer
A. 1.55
Explanation
The specific gravity of a liquid is defined as the ratio of its density to the density of water. Since the mass density of the given liquid is 1550 kg/m2, we can compare it to the density of water, which is approximately 1000 kg/m2. Dividing the mass density of the liquid by the density of water, we get 1550/1000 = 1.55. Therefore, the specific gravity of the liquid is 1.55.
19.
Calculate the pressure produce by a force of 800N acting on an area of 2.0m2
Correct Answer
B. 400Pa
Explanation
The pressure produced by a force on an area can be calculated using the formula: pressure = force/area. In this case, the force is given as 800N and the area is given as 2.0m2. By substituting these values into the formula, we get: pressure = 800N/2.0m2 = 400Pa. Therefore, the correct answer is 400Pa.
20.
A concrete slab 1.0m by 0.5m by 0.1m has a mass of 120kg. What is the density of concrete?
Correct Answer
A. 2400 kg/m3
Explanation
The density of a substance is calculated by dividing its mass by its volume. In this case, the mass of the concrete slab is given as 120 kg and its volume can be calculated by multiplying its length, width, and height (1.0m x 0.5m x 0.1m = 0.05 m3). Dividing the mass by the volume gives us a density of 2400 kg/m3.