Question

A heart defibrillator is used to enable the heart to start beating if it has stopped. This is done by passing a large current of 12 A through the body at 21 V for a very short time, usually about 3.4 ms .

What power does the defibrillator deliver to the body?

How much energy is transferred?

Answer 1

Current passing through the body = I = 12 A

Voltage applied = V = 21 V

Time period = t = 3.4 ms = 3.4 x 10^-3 sec

Power the defibrillator delivers to the body = P

P = VI

P = (21)(12)

P = 252 W

Energy transferred to the body = E

E = Pt

E = (252)(3.4x10^-3)

E = 0.857 J

a) Power the defibrillator delivers to the body = 252 W

b) Energy transferred to the body = 0.857 J