1.

A 50 V battery is supplying current of 10 A when connected to a resistor. If the efficiency of the battery at this current is 25%, then the internal resistance of the battery isA. `2.5 Omega`B. ` 3.75 Omega`C. `1.25 Omega`D. `5 Omega`

Answer» Correct Answer - B
b. `50 = 10[R+r]`
or `R + r = 5 Omega`
` eta = R/(R+r) or 0.25 = R/(R+r)`
`R + r = 4R `
or `r = 3R`
Then `R = 5//4 = 1.2 Omega and r = 3.75 Omega` .


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