http://www.ck12.org Chapter 16. Electric Potential
16.5 Electrical Energy Storage
Objectives
The student will:
- Understand how energy is stored in a capacitor.
- Solve problems involving energy stored in capacitors.
Introduction
A capacitor stores electrical energy within the electric field between its plates. Otherwise, there would be no energy
for the electrical discharge for such things as camera flashes. The ability of capacitors to store and release energy is
one of their most important attributes and is directly related to the functioning of most electronic devices. Recall that
we described the effect of electrical resonance between a capacitor and a coiled wire in a crystal radio set,Figure
16.16. The effect occurs because the capacitor is able to store and release energy many hundreds of thousands of
times (for AM radio) per second through the coiled wire. The same effect is true for modern radios, televisions,
computers, and cell phones. Any electrical device that receives a signal requires that capacitors store and release
energy.
FIGURE 16.16
A crystal radio set.How Energy is Stored in Capacitors
Energy is stored in a capacitor when work is done by the battery in removing electrons from one plate (the positive
plate) and depositing them on the other plate (the negative plate) of the capacitor. A capacitor cannot be charged
instantaneously. As more charge is added to each plate of the capacitor, the battery must do increasingly more work