A defibrillator is a device used to shock the heart back to normal beat patterns

Question

A defibrillator is a device used to shock the heart back to normal beat patterns. To do this, it discharges a 12 ?F capacitor through paddles placed on the skin, causing charge to flow through the heart. Assume that the capacitor is originally charged with 4.0 kV .

Part A

What is the charge initially stored on the capacitor?

Part B

What is the energy stored on the capacitor?

Part C

If the resistance between the two paddles is 100 ? when the paddles are placed on the skin of the patient, how much current ideally flows through the patient when the capacitor starts to discharge?

Part D

If a defibrillator passes 20 A of current through a person in 60 ?s . During this time, how much charge moves through the patient?

Explanation / Answer

I am assuming that capacitance is in uF as the symbol is missing....Let me know if its different, I will change accordingly. Let me know if you have any doubt....Please ask

(a) Q = C*V

Q = 12 uF * 4 kV

Q = 12e-6*4e3

Q = 0.048 C

OR, Q = 4.8e-2 C

(b) E = Q2 / 2C

E = 0.0482 / 2*12e-6

E = 96 J

(c) Is the resistance 100 ohms ???

Use ohm's law

V = IR

I = V/R = 4000/100 = 40 amps

(d) I = Q/t

Q = I*t ( What is time's unit ???)

Just multiply given current by time ( convert time to seconds) to get charge. It's very easy

Q =

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