Capacitors  Multiple ChoiceQ1. A 1μF capacitor is charged using a constant current of 10 μA for 20 s. What is the energy finally stored by the capacitor?
Q2. A capacitor of capacitance 10 μF is fully charged through a resistor R to a p.d. of 20V using the circuit shown below. Which one of the following statements is incorrect?
Q3. A 10 mF capacitor is charged to 10V and then discharged completely through a small motor. During this process, the motor lifts a weight of mass 0.10 kg. If 10 % of the energy stored in the capacitor is used to lift the weight, through what approximate height will the weight be lifted?
Q4. A capacitor of capacitance 15 μF is fully charged and the potential difference across its plates is 8.0V. It is then connected into the circuit as shown below. The switch S is closed at time t = 0. Which one of the following statements is correct?
Q5. A capacitor of capacitance C discharges through a resistor of resistance R. Which one of the following statements is not true?
Q6. In the circuit shown below, the capacitor C is charged to a potential difference V when the switch S is closed. Which line, A to D, in the table gives a correct pair of graphs showing how the charge and current change with time after S is closed?
Q7. The graph shows how the charge stored by a capacitor varies with the potential difference across it as it is charged from a 6V battery. Which one of the following statements is not correct?
Q8. A capacitor of capacitance C stores an amount of energy E when the pd across it is V. Which line, A to D, gives the correct stored energy and pd when the charge is increased by 50% ?
Q10. A voltage sensor and a datalogger are used to record the discharge of a 10 mF capacitor in series with a 500Ω resistor from an initial pd of 6.0V. The datalogger is capable of recording 1000 readings in 10s. Which line, A to D, in the table gives the pd and the number of readings made after a time equal to the time constant of the discharge circuit?
Q11. When switch S in the circuit is closed, the capacitor C is charged by the battery to a pd V_{0}. Which graph best shows how the pd across the capacitor varies with time, t, after S is opened?
How long can the
capacitor be used for before it must be recharged?
Q13. When a capacitor discharges through a resistor it loses 50% of its charge in 10 s. What is the time constant of the capacitorresistor circuit?
Q14. An uncharged capacitor of fixed capacitance is connected in series with a switch and battery. The switch is closed at time t = 0. Which graph, A to D, shows how the energy, E, stored by the capacitor, changes with time, t, after the switch is closed?
Q15.The voltage across a capacitor falls from 10 V to 5 V in 48 ms as it discharges through a resistor. What is the time constant of the circuit?
Q16. The graph shows how the charge stored by each of two capacitors, X and Y, increases as the pd across them increases. Which one of the following statements is correct?
Q17. A 1000 μF capacitor and a 10 μF capacitor are charged so that the potential difference across each of them is the same. The charge stored in the 1000 μF capacitor is Q_{1} and the charge stored in the 10 μF capacitor is Q_{2}. What is the ratio Q_{1}/Q_{2}?
Q18. The graph shows how the potential difference across a capacitor varies with the charge stored by it. Which one of the following statements is correct?
Q19. An initially uncharged capacitor of capacitance 10 μF is charged by a constant current of 200 μA. After what time will the potential difference across the capacitor be 2000V?
Q20. A 1000 μF capacitor, X, and a 100 μF capacitor, Y, are charged to the same potential difference. Which row, A to D, in the table gives correct ratios of charge stored and energy stored by the capacitors?

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