Question

A battery has an emf of 15.0 V. The terminal voltage of the battery is 11.2 V when it is delivering 26.0 W of power to an external load resistor R.

(a) What is the value of R?

(b) What is the internal resistance of the battery?

Answers

Sonny
The volts across your load resistor = 11.2V
Power delivered = 26.0 W
Power = Volts x Amps so Current (Amps) = 26.0/11.2 V = 2.32A

(A) 11.2V/2.32A = 4.83 ohm

Volts lost across internal resistance = 15 - 11.2 = 3.8V

Internal resistance = Lost Volts/Current = 3.8/2.32 = 1.64 ohms (B)

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