# Design a Capacitor

1. Feb 15, 2009

### cfl25

1. The problem statement, all variables and given/known data
You are to design a capacitor capable of providing the energy required to start a small motor. In particular, the capacitor must meet the following three requirements
a) The capacitor must provide an average power of 10W for a time interval of 0.50 seconds
b/ Macimum allowable Capacitor potential difference = 12V

2. Relevant equations
C = Q/V

3. The attempt at a solution
I am kinda stumped on the average power 10W over 0.5 seconds. Does that mean that i convert back into Energy of 5J or something else?

2. Feb 15, 2009

### skeptic2

You're missing a relevant equation. Look for one that defines energy in terms of capacitance and voltage.

3. Feb 15, 2009

### cfl25

u = (1/2)cv² ?

4. Feb 15, 2009

### skeptic2

That's it.

5. Feb 17, 2009

### cfl25

is there an equation or an explanation that will help me understand the values if the plates are a foil and rolled together, so it keeps the area needed at a reasonable size?