How Do You Calculate Battery Internal Resistance from Load Conditions?

[ul44]

Homework Statement

I have been stuck on the following problem for 2 days now, can anyone help?

The p.d. at the terminals of a battery is 25V when no load is connected and 24V when a load taking 10A is connected. Determine the internal resistance of the battery...

Thanks

Homework Equations

The Attempt at a Solution

 

[vk6kro]

https://www.physicsforums.com/attachment.php?attachmentid=23048&d=1263424328

In this diagram, (load present, but not shown) what is the voltage across the resistor?

What current is flowing in it?

So, what is the value of the resistor?

This is the equivalent circuit of a battery. When there is no load, the voltage across the internal resistance is zero, so the voltage at the terminals is 25 volts. When there is 10 amps flowing, a voltage is dropped across the internal resistance, so the output is 24 volts.
These voltages are relative to the negative terminal.