How Do You Calculate Battery Internal Resistance from Load Conditions?

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SUMMARY

The internal resistance of a battery can be calculated using the terminal voltage measurements under load conditions. In this case, the battery shows a terminal voltage of 25V with no load and 24V when a 10A load is applied. The internal resistance is determined by the voltage drop across the internal resistance when the load is connected. Using the formula for internal resistance (R = (V_no_load - V_load) / I_load), the internal resistance is calculated to be 0.1 ohms.

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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

 
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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?

internal resist.PNG


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.
 

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