Homework Help: EMF's in series how does this work ?

1. Jul 4, 2008

hilly

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

A secondary cell having an e.m.f. of 2V and an internal resistance of 1ohm is connected in series with a primary cell having an e.m.f. of 1.5V and an internal resistance of 100ohm the negative terminals of each cell is connected to the positive terminal of the other cell. A voltmeter having a resistance of 50ohm is connected to measure the terminal volatage of the cells. Calculate the voltmeter reading and the current in each cell.

Ans given by book:72.8mA, 34.3mA, 1.93V

2. Relevant equations
Kirchoff voltage law.

3. The attempt at a solution

I can not understand how 2 cells in series can have a different current ? What concept am I missing ?

2. Jul 4, 2008

zeitghost

The current will change according to which cell voltage you are measuring.

The voltmeter has a resistance of 50R... (that's some "voltmeter"...)

3. Jul 4, 2008

Defennder

Is there a picture for the question? I'm not sure how the voltmeter is connected to measure the terminal voltage.

4. Jul 4, 2008

hilly

Sorry no picture because the textbook has no picture only the words

5. Jul 4, 2008

hilly

The book answer gives one voltage and 2 currents.

6. Jul 4, 2008

Redbelly98

Staff Emeritus
Instead of thinking about 2 batteries in series, try picturing the situation as 3 objects all in parallel (the 2 cells and the 50-ohm resistor).

Don't forget to include the internal resistances as part of the cells.