# Potential difference between plates

1. Jul 12, 2008

### kdrobey

1. The problem statement, all variables and given/known data
he electronic flash attachment for a camera contains a capacitor for storing the energy used to produce the flash. In one such unit, the potential difference between the plates of a 705 µF capacitor is 320 V.

(a) Determine the energy that is used to produce the flash in this unit. _____J
(b) Assuming that the flash lasts for 5.0 multiplied by 10-3 s, find the effective power or "wattage" of the flash. _______W

2. Relevant equations
Energy=1/2CV^2

3. The attempt at a solution
.5(7.05 x 10^-6 F)(320V)^2. this gave me .3606, which was not the correcct answer for part A

2. Jul 12, 2008

### Staff: Mentor

Is the capacitance 705 µF or 7.05 µF?

3. Jul 12, 2008

### kdrobey

it's 705 uF. i thought i was supposed to convert uF to F. (1F=10^-6uf?)

4. Jul 12, 2008

### Staff: Mentor

Right. But you also "converted" 705 to 7.05 for some reason.

5. Jul 12, 2008

### kdrobey

ohhh i see. so (705 x 10^-6)*(302)^2=36.096?

6. Jul 13, 2008

### Defennder

Yet another typo. Is it 302 V or 320 V?