At t = 0 the switch S is closed with the capacitor uncharged.If C = 40 $\mu$F,$\varepsilon$ = 50 V,and R = 5.0 k$\Omega$,how much energy is stored by the capacitor when I = 2.0 mA?
A)20 mJ
B)28 mJ
C)32 mJ
D)36 mJ
E)40 mJ

Question

At t = 0 the switch S is closed with the capacitor uncharged.If C = 40 $\mu$F,$\varepsilon$ = 50 V,and R = 5.0 k$\Omega$,how much energy is stored by the capacitor when I = 2.0 mA? 
A)20 mJ 
B)28 mJ 
C)32 mJ 
D)36 mJ 
E)40 mJ

Quizplus · Accepted Answer

The energy stored in a capacitor is given by the formula U = 1/2 * C * V^2, where U is the energy stored, C is the capacitance, and V is the voltage across the capacitor.

First, we need to find the voltage across the capacitor. Since the current through the circuit is I = V/R, we can find that V = I * R = (2.0 mA) * (5.0 kΩ) = 10 V.

Using the formula for energy stored, we can find that U = 1/2 * (40 μF) * (10 V)^2 = 32 mJ.

Therefore, the answer is C) 32 mJ.

At T = 0 the Switch S Is Closed with the Capacitor