The electrical signals to the heart are typically coordinated to create a wave o

Question

The electrical signals to the heart are typically coordinated to create a wave of compression that travels across the heart to pump the blood through the heart chambers. If these signals get misaligned, the bits of the heart muscle vibrate independently and as a result do not move blood. This situation is called fibrillation and can quickly lead to death.

A. How much charge (Q) is stored on each plate of the capacitor when it is fully charged and how much energy (E) does it store?
Q = --------- C
E = ---------- J

D. Calculate the effective resistance, R, of the path of the current through the body.
---------

If the situation is caught in time, passing a jolt of current through the heart can realign the electrical signals in the heart and start it beating again. The device that delivers this current is a defibrillator. (See the figure at the right.) The heart of a heart defibrillator is a big capacitor. A battery takes perhaps half a minute to charge this capacitor. This capacitor has a capacitance of 54 F (microFarads) and, when turned on, is charged by a battery to 4,200 Volts.

Explanation / Answer

Here

A)

Q = 54 *10^-6 * 4200 V

Q = 0.227 C

E = 0.50 * C * V^2

E = 0.50 * 54 *10^-6 * 4200^2

E= 476.3 J

B)

average current = Q/time

average current = 0.227/.10

average current = 2.27 A

C)

as P = V * I

476.3/0.10 = 2.27 * V

V = 2098 V

the potential difference is 2098 V

D)

R = V/I

R = 2098/2.27 Ohm

R = 924 Ohm

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