# Experiment to find out emf of the battery

1. Mar 19, 2016

### Gajan1234

I conducted an experiment to find out the emf of a battery, the result turned out to be 1.35 volts , however on the battery, it says the battery is 1.5 voltage.

Does it mean that my method is wrong or less accurate. But I used three different methods:

1) measuring the terminal voltage across the battery when there is no current going through the battery

2) Measuring the voltage when the current changes and then ploting the graph to finf the y intercept

3) using the formula r= V1-V2/I2-I1

All of those method gave me approximately 1.35 volts.

2. Mar 19, 2016

### Buzz Bloom

Hi Gajan:

Batteries tend to lose their voltage as they are used over time. Therefore an old battery may fail to have the voltage it had when it was new. Do you have a brand new battery you can test?

Regards,
Buzz

3. Mar 19, 2016

### Gajan1234

It makes much more sense, I didnt think in that way and yh I did use a old battery so it makes sense

4. Mar 19, 2016

### meBigGuy

It is good to understand the discharge curve for any battery you are studying or experimenting with. For example for an AA alkaline, here is are some typical discharge curves for batteries from different manufacturers ( for example RS = radio shack) (from http://www.powerstream.com/AA-tests.htm)

The curves will be different for different currents. The Amp Hours (AH) rating is always at a specific constant discharge current.