The flash unit in a camera uses a 2.0 V battery to charge a capacitor. The capac

Question

The flash unit in a camera uses a 2.0 V battery to charge a capacitor. The capacitor is then discharged through a flashlamp. The discharge takes 10s, and the average power dissipated in the flashlamp is 10 W.

Part A

What is the capacitance of the capacitor?

A vacuum-insulated parallel-plate capacitor with plate separation d has capacitance C0.

Part A

What is the capacitance if an insulator with dielectric constant and thickness d/2 is slipped between the electrodes? Assume plate separation is unchanged.

Express your answer in terms of the variables d, C0, and .

The flash unit in a camera uses a 2.0 V battery to charge a capacitor. The capacitor is then discharged through a flashlamp. The discharge takes 10s, and the average power dissipated in the flashlamp is 10 W.

Part A

What is the capacitance of the capacitor?

Explanation / Answer

1. Power = E/dt

E = energy stored in capacitor

E = P*dt = 10*10*10^-6 = 10^-4 J

E = 0.5*CV^2

C = 2*E/V^2

C = 2*10^-4/(2^2) = 5*10^-5 C

C = 50 uF

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