Question

A current of 2a flows through a 2 ohm resistor when connected across a battery , the same battery supplies a current of 0.5a when connected across a 9 ohm resistor . the internal resistance of the battery

Answer 1

Let the internal resistance of the battery be r
Now,
The potential of the battery is constant or in other words the emf supplied by the battery will be same (No matter the amount of resistance connected)

So,
V1 = V2
2(r+ 2)= 0.5(r+ 9)
2r + 4 = 0.5 r + 4.5
1.5r = 0.5
r=1/3
r=0.33 ohm

So,
The internal resistance of the battery is 0.33ohm

Answer 2

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