A 20.0-$\mu$F capacitor is charged to 200 V and is then connected across a 1000-$\Omega$ resistor.What is the initial current just after the capacitor is connected to the resistor?
A)100 mA
B)200 mA
C)150 mA
D)300 mA
E)50 mA

Question

Quizplus · Accepted Answer

The initial current (I) just after the capacitor is connected to the resistor can be calculated using Ohm's law and the formula for the time constant of an RC circuit. 
The time constant (τ) of the circuit is given by τ = RC = 1000 F1F1F1S1F1F1F10 * 20.0-F1F1F1S1F1F1F10F = 20 * 10^-3 seconds.
The initial current can be calculated using I = V/R (1 - e^-t/τ), where V is the initial voltage of 200V and t is 0 (just after the capacitor is connected). 
I = 200V/1000 F1F1F1S1F1F1F10 * (1 - e^0/20*10^-3) 
I = 200 mA. 
Therefore, the best choice is B, 200 mA.

A 200- μ\muμ F Capacitor Is Charged to 200 V and Is Then

A 200- $\mu$ F Capacitor Is Charged to 200 V and Is Then