1.
Charge of 60 C passes through an electric lamp in 2 minutes.
Then the current in the lamp is
Correct Answer
A. 0.5 A
Explanation
The current in the lamp can be calculated by dividing the charge passing through it by the time taken. In this case, the charge is given as 60 C and the time is given as 2 minutes. Converting the time to seconds (2 minutes = 120 seconds), we can calculate the current as 60 C / 120 s = 0.5 A. Therefore, the current in the lamp is 0.5 A.
2.
The material through which electric charge can flow easily is
Correct Answer
A. Copper
Explanation
Copper is a good conductor of electricity, meaning it allows electric charge to flow easily through it. This is due to its atomic structure, which allows for the movement of electrons. Copper is commonly used in electrical wiring and circuitry because of its high conductivity. Germanium, quartz, and mica are not as good conductors as copper, so they do not allow electric charge to flow as easily.
3.
The current flowing in a conductor is proportional to
Correct Answer
A. Drift velocity
Explanation
The current flowing in a conductor is proportional to drift velocity because drift velocity is the average velocity at which free electrons move in a conductor due to an applied electric field. As more electrons move with a higher drift velocity, the overall current in the conductor increases. Therefore, the greater the drift velocity, the greater the current flowing in the conductor.
4.
A toaster operating at 240V has a resistance of 120Ω. The power is
Correct Answer
A. 480 W
Explanation
The power of an electrical device can be calculated using the formula P = V^2/R, where P is power, V is voltage, and R is resistance. In this case, the voltage is given as 240V and the resistance is given as 120Ω. Plugging these values into the formula, we get P = (240^2) / 120 = 480W. Therefore, the correct answer is 480W.
5.
If the length of a copper wire has a certain resistance R, then on doubling the length its specific resistance
Correct Answer
A. Will remain the same
Explanation
The specific resistance of a material is a constant property that depends on the material itself, not on its length. Therefore, doubling the length of a copper wire will not change its specific resistance.
6.
When two 2Ω resistances are in parallel, the effective resistance is
Correct Answer
A. 1 Ω
Explanation
When two resistances are in parallel, the effective resistance is given by the formula 1/Reff = 1/R1 + 1/R2. In this case, both resistances are 2Ω. Plugging in the values, we get 1/Reff = 1/2Ω + 1/2Ω = 2/2Ω = 1Ω. Therefore, the effective resistance when two 2Ω resistances are in parallel is 1Ω.
7.
In the case of insulators, as the temperature decreases, resistivity
Correct Answer
A. Increases
Explanation
As the temperature decreases in the case of insulators, the resistivity increases. This is because insulators have a large energy band gap between their valence band and conduction band. At higher temperatures, more electrons are able to gain enough energy to jump from the valence band to the conduction band, allowing for better conductivity. However, as the temperature decreases, the number of electrons with enough energy decreases, leading to a decrease in conductivity and an increase in resistivity.
8.
If the resistance of a coil is 2 Ω at and α = 0.004 /, then its
resistance at is
Correct Answer
A. 2.8 Ω
Explanation
The resistance of a coil is directly proportional to its temperature coefficient, which is represented by the symbol α. In this case, the temperature coefficient α is given as 0.004 /°C. Since the temperature is not provided in the question, we can assume that it remains constant. Therefore, if the resistance at is 2 Ω, the resistance at will be 2 Ω * (1 + α * ΔT), where ΔT is the change in temperature. Since ΔT is not given, we can assume it to be 0, which means there is no change in temperature. Therefore, the resistance at will be 2 Ω * (1 + 0.004 * 0) = 2 Ω. Thus, the correct answer is 2 Ω.
9.
According to Faraday’s law of electrolysis, when a current is
passed, the mass of ions deposited at the cathode is independent of
Correct Answer
A. Resistance
Explanation
According to Faraday's law of electrolysis, the mass of ions deposited at the cathode is independent of resistance. This means that the amount of substance deposited during electrolysis is determined by the quantity of charge passing through the electrolyte, rather than the resistance of the circuit. In other words, the mass of ions deposited at the cathode is directly proportional to the amount of electric charge passing through the electrolyte, regardless of the resistance in the circuit.
10.
When n resistors of equal resistances (R) are connected in series,
the effective resistance is
Correct Answer
A. NR
Explanation
When n resistors of equal resistances (R) are connected in series, the effective resistance is the sum of the resistances of all the resistors. Since all the resistors have the same resistance (R), the effective resistance would be n times the resistance of each resistor (R). Therefore, the correct answer is nR.