Capacitor - charging and discharge

A 10^-4 F capacitor is connected to a 10 V cell. What is the charge and energy stored on the capacitor?

• A

• B

• C

• D

The formula τ = RC can be used to find the time constant for the discharge of a capacitor through a resistor. The capacitor is initially charged to a potential of 1 V.

At a time t = τ, what is the voltage in volts across the capacitor?

• e

• e^-1

• 0.5

• 0

Which of the following graphs best shows the potential difference across a capacitor discharging through a resistor?

• A

• B

• C

• D

Which of the following graphs best shows the potential difference across a capacitor charging through a resistor?

• A

• B

• C

• D

The energy stored in a capacitor is E when charged to a voltage V₀. After a time τ the potential difference across the capacitor has fallen to 0.69 V₀ as it discharges through a resistor. This means that the energy transferred to the resistor in this time will be:

• 0.31 E

• 0.69² E

• (1 - 0.69²) E

• 0.31² E

A capacitor discharges through a fixed resistor. The time constant τ for the capacitor and resistor is 10 seconds. At what time will the charge across the capacitor have dropped to half the original value?

• 0.5 e^-10

• 10 e^-0.5

• 10 ln(-0.5)

• -10 ln(0.5)

A capacitor discharge circuit of time constant 45 ms includes a capacitor and resistor. The capacitor has a capacitance of 18 µF.

What is the resistance of the resistor?

• 2.5 x 10³ Ω

• 2.5 Ω

• 0.40 Ω

• 4.0 x 10^-4 Ω

Which of the following is symbol of capacitor ?

• 
• 
• 
• 

When 3 capacitors are arranged in parallel , the equivalent capacitance is

• C_eq = C₁ + C₂ + C₃

• C_eq = 1/C₁ + 1/C₂ + 1/C₃

• C = QV₁ + QV₂ + QV₃

• 1/C_eq = 1/C₁ + 1/C₂ + 1/C₃

When 3 capacitors are arranged in series , the equivalent capacitance C is

• C_eq = C₁ + C₂ + C₃

• 1/C_eq = 1/C₁ + 1/C₂ + 1/C₃

• C_eq = QV₁ + QV₂ + QV₃

• C_eq = CR₁ + CR₂ + CR₃