# Homework Help: Defibrillator current physics problem

1. Apr 17, 2004

### moonlit

I have two physics problems that I'm not sure how to do, can someone help me?

1) A defibrillator is used during a heart attack to restore the heart to its normal beating pattern. A defibrillator passes 16 A of current through the torso of a person in 1.6 ms. (a) How much charge moves during this time? (b) How many electrons pass through the wires connected to the patient?

2) A resistor is connected across the terminals of a 9.0-V battery, which delivers 2 x 105 J of energy to the resistor in 4 hours. What is the resistance of the resistor?

Should I use the equation delta q=I(delta t) for both these problems?

2. Apr 17, 2004

### chroot

Staff Emeritus
The first one is just $\Delta Q = I \Delta t$.

The second one involves the definition of power, namely

$$P = \frac{d E}{d t} = \frac{V^2}{R}$$.

- Warren

3. Apr 17, 2004

### moonlit

So the answer to part A would be .01 C correct? What about part B?

4. Apr 17, 2004

### chroot

Staff Emeritus
5. Apr 17, 2004

### moonlit

Ok, not sure what to do with part b. P=E/T so wouldn't that be .01? Also, how do I convert amps to volts?

Last edited: Apr 17, 2004
6. Apr 17, 2004

### chroot

Staff Emeritus
7. Apr 17, 2004

### paul11273

Moonlit-
When you first mentioned you were not sure what to do with part (b), I think you were referring to the second part of question #1.

If that is correct, than to find the number of electrons that pass through one of the electrodes, you divide the total charge (what you found in part a) by the charge of each electron.

Number of Electrons = Total Charge / Elementary Charge
n = Q/e
n = .0256C / 1.6*10^-19C
n = 1.6*10^17 electrons

8. Apr 17, 2004

### chroot

Staff Emeritus
I apologize, even though you were talking about part b, I was thinking about question 2!

- Warren