Peoples Physics Book Version-2

http://www.ck12.org Chapter 14. Electric Circuits Version 2

d) To find the charge stored in the capacitor we will use the equation

Q=CV

First we must convert the capacitor into the correct units for the equation. Then we can substitute in the values and
solve for the charge stored.

20 μF×

1F

1000000 μF

= 2. 0 × 10 −^5 F

Q=CV= 2. 0 × 10 −^5 F×18V= 3. 6 × 10 −^4 C

e) The potential energy stored in a capacitor is

U=

1

2

CV^2

All we need to do is plug in the known values and get the potential energy.

U=

1

2

CV^2 =

1

2

× 2. 0 × 10 −^5 F×(18V)^2 = 3. 2 × 10 −^3