(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A capacitor, previously charged by a 1000 V source, is discharged through a photographic flash unit. The capacitor delivered an average power of 1000 W and the flash lasts 0.040 s. What is the estimated capacitance of the capacitor

a. 40 x 10^{-6}F

b. 20 x 10^{-6}F

c. 60 x 10^{-6}F

d. 80 x 10^{-6}F

e. 80 x 10^{-3}F

2. Relevant equations

Q = CV

W = 1/2 QV

P = VI

Q = I t

3. The attempt at a solution

I got two different answers....

1.

P = W/t = CV^{2}/ 2t

C = 2 Pt / V^{2}= 80 x 10^{-6 }F (d)

2.

P = VI = VQ/t = CV^{2}/ t

C = 40 x 10^{-6}F (a)

Something's definitely wrong with my concept but I don't know what...

Thanks

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# Homework Help: Capacitance of capacitor

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