When a capacitor has a charge of magnitude 80 μC on each plate the potential difference across the plates is 16 V. How much energy is stored in this capacitor when the potential difference across its plates is 42 V?
A) 1.0 mJ
B) 4.4 mJ
C) 3.2 mJ
D) 1.4 mJ
E) 1.7 mJ

Question

Quizplus · Accepted Answer

The energy stored in a capacitor is given by the formula $E = \frac{1}{2}CV^2$, where $E$ is the energy in joules, $C$ is the capacitance in farads, and $V$ is the potential difference in volts. To find the capacitance, we use the initial condition: $C = \frac{Q}{V} = \frac{80 \times 10^{-6} C}{16 V} = 5 \times 10^{-6} F$. Then, using the new potential difference of 42 V, the energy stored is $E = \frac{1}{2} \times 5 \times 10^{-6} F \times (42 V)^2 = 4.41 \times 10^{-3} J = 4.4 mJ$.

When a Capacitor Has a Charge of Magnitude 80 μC