An air-filled 20-μF capacitor has a charge of 60 μC on its plates.How much energy is stored in this capacitor?

Question

Quizplus · Accepted Answer

The energy stored in a capacitor is given by the formula: 
E = 1/2 CV^2, 
where E is energy, C is capacitance, and V is voltage. 
We can first use the formula for capacitance: 
C = Q/V, 
where Q is charge and V is voltage. 
Solving for V: 
V = Q/C = (60 μC)/(20 μF) = 3 V 
Now we can plug in V and C into the energy formula: 
E = 1/2 (20 μF) (3 V)^2 = 90 μJ 
Therefore, the answer is C.

An Air-Filled 20-μF Capacitor Has a Charge of 60 μC