# Finding internal resistor.

1. May 13, 2012

### helper-

1. The problem statement, all variables and given/known data

Helping someone regarding this Qns:

A Battery is formed by four 1.5 V identical cell in series. When a external resistor of 31 Ohm is connected across he battery, the current is 280 mA. Find the internal resistor of each cell.

Can someone help to solve pls?

2. Relevant equations

V = E - Ir ?

3. The attempt at a solution

Last edited: May 13, 2012
2. May 13, 2012

### rude man

No, try R = E/i

3. May 13, 2012

### helper-

R = e / i = 6V / 0.290A = 21.43 Ohms

**is this is less than the load resistance of 31 Ohms?

The answer given is 0.19 Ohms; but unable to solve. Any idea?

4. May 13, 2012

### rude man

It's 0.290 A, not 0.280.

What limits the current thru the 31 ohm resistor?

5. May 13, 2012

### truesearch

something wrong here !!!! 6V emf, current of 0.28A means total R = 6/0.28 =21.4 ohms
Does not fit with external resistance of 31 ohms connected.
Check the question

6. May 13, 2012

### rude man

That's right, it's impossible.

7. May 14, 2012

### helper-

*opps type on the 0.28.

Thanks all! Guess have to check with the lecturer, seems the qns is wierdddd. (: