EE-Quiz Question 2

Faraday's Bath

Figure 1	Figure 2

Figure 1:
An oil-filled capacitor consists of two plates separated by a dielectric made of oil with a dielectric constant of 10. The capacitance is 10µF and it is charged to 10 volts.

Figure 2:
The oil is drained, leaving air between the plates. The capacitance falls to 1µF.

Questions:

1. What is the voltage across the capacitor in Figure 2?

2. Extra credit: What is the energy stored by the capacitor in Figure 1? In Figure 2? If the energy changed, where did the extra energy come from or go to?

3. More extra credit: Under what circumstance would there be no change in energy stored in the capacitor?

Answers