What is the energy (in J) stored in the 23.0 µF capacitor of a heart defibrillator charged to 7.40 ✕ 103 V?

629.7 J = 0.63 kJ.

Explanation:

Charge and voltage are related to the capacitance C of a capacitor by Q = CV, and so the expression for Ecap can be written mathematically into three equivalent expressions:

Ecap = QV^2

= 1/2 * (C*V^2)

= 1/2 * Q^2/C

where,

Q = charge

V = voltage on a capacitor C.

The energy is in joules for a charge in coulombs, voltage in volts, and capacitance in farads.

Given:

C = 23.0 µF

= 2.3 x 10^-5 F

V = 7.40 ✕ 10^3 V

Ecap = 1/2 * (C*V^2)

= 1/2 * (2.3 x 10^-5) * (7.40 ✕ 10^3)^2

= 629.7 J

= 0.63 kJ.