8.3 Energy Stored in a Capacitor

The potential difference across a 5.0-pF capacitor is 0.40 V. (a) What is the energy stored in this capacitor? (b) The potential difference is now increased to 1.20 V. By what factor is the stored energy increased?

A capacitor has a charge of $2.5 \mu \text{C}$ when connected to a 6.0-V battery. How much energy is stored in this capacitor?

(a) What is the energy stored in the $10.0 - \mu \text{F}$ capacitor of a heart defibrillator charged to $9.00 \times 10^{3} \text{V}$ ? (b) Find the amount of the stored charge.

A $165 - \mu \text{F}$ capacitor is used in conjunction with a dc motor. How much energy is stored in it when 119 V is applied?

An anxious physicist worries that the two metal shelves of a wood frame bookcase might obtain a high voltage if charged by static electricity, perhaps produced by friction. (a) What is the capacitance of the empty shelves if they have area $1.00 \times 10^{2} \text{m}^{2}$ and are 0.200 m apart? (b) What is the voltage between them if opposite charges of magnitude 2.00 nC are placed on them? (c) To show that this voltage poses a…

Suppose that the capacitance of a variable capacitor can be manually changed from 100 pF to 800 pF by turning a dial, connected to one set of plates by a shaft, from $0 °$ to $180 °$. With the dial set at $180 °$ (corresponding to $C = 800 \text{pF}$), the capacitor is connected to a 500-V source. After charging, the capacitor is disconnected from the source, and the dial is turned to $0 °$. If friction is negligible, how much work is…