- #1
songoku
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Homework Statement
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
Homework Equations
Q = CV
W = 1/2 QV
P = VI
Q = I t
The Attempt at a Solution
I got two different answers...
1.
P = W/t = CV2 / 2t
C = 2 Pt / V2 = 80 x 10-6 F (d)
2.
P = VI = VQ/t = CV2 / t
C = 40 x 10-6 F (a)
Something's definitely wrong with my concept but I don't know what...
Thanks