Capacitor discharge and time constants
Question 70S: Short Answer

1. A 250 mF capacitor is charged through a 100 kW  resistor.
	Calculate the time constant of the circuit.

2.	The initial current is 100 mA. What is the current after 30 s?

3.	Suggest values of R and C which would produce RC circuits with time constants of 1.0 s and 20 s.

4.	A 10 mF capacitor is charged to a potential difference of 20 V and then isolated. If its leakage resistance is 10 MW, how long will it take for the charge to fall to 100 mC?

5. A 100 mF capacitor is charged and connected to a digital voltmeter (which has effectively infinite resistance). The p.d. measured across the capacitor falls to half its initial value in 600 s.  Calculate the time constant of the discharge process.

6.	Calculate the resistance of the capacitor insulation.

Capacitor discharge and time constants
Question 70S: Short Answer

1. A 250 mF capacitor is charged through a 100 kW  resistor.
	Calculate the time constant of the circuit.

2.	The initial current is 100 mA. What is the current after 30 s?

3.	Suggest values of R and C which would produce RC circuits with time constants of 1.0 s and 20 s.

4.	A 10 mF capacitor is charged to a potential difference of 20 V and then isolated. If its leakage resistance is 10 MW, how long will it take for the charge to fall to 100 mC?

5. A 100 mF capacitor is charged and connected to a digital voltmeter (which has effectively infinite resistance). The p.d. measured across the capacitor falls to half its initial value in 600 s.  Calculate the time constant of the discharge process.

6.	Calculate the resistance of the capacitor insulation.