The flash unit in a camera uses a 80 V battery to charge a c

The flash unit in a camera uses a 8.0 V battery to charge a capacitor. The capacitor is then discharged through a flashlamp. The discharge takes 10mus, and the average power dissipated in the flashlamp is 10 W. What is the capacitance of the capacitor? Express your answer with the appropriate units.

Solution

P_avg = delta E / delta t

delta E = P_avg * delta t

= 10 * 10 * 10^-6 = 10^-4 J

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delta E = 1/2 Q V = 1/2 C V²

C = Q / V

C = 2 * delta E /  V²

= 2 * 10^-4 / 8²

C = 3.12 * 10^-6 F