Charging and discharging capacitors Quiz
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5 questions, one answer each
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1. What is the time constant of a 470 μF capacitor in series with a 22 kΩ resistor?
- A. 0.021 s
- B. 10 s
- C. 47 s
- D. 1.0 × 10⁷ s
2. After a time equal to 2RC, what fraction of the initial charge remains on a discharging capacitor?
- A. e⁻¹ (37%)
- B. 1/2
- C. e⁻⁴ (1.8%)
- D. e⁻² (14%)
3. A graph of ln V against t for a discharging capacitor has a gradient of −0.25 s⁻¹. What is the time constant?
- A. 4.0 s
- B. 0.25 s
- C. −4.0 s
- D. 0.50 s
4. Which statement about charging a capacitor through a resistor is correct?
- A. The current is zero at the start
- B. The current is largest at the start and falls to zero
- C. The current is constant throughout
- D. The current increases as the capacitor charges
5. The resistance in a discharge circuit is doubled while C is unchanged. What happens to the time constant?
- A. It is halved
- B. It is unchanged
- C. It is doubled
- D. It is quadrupled