# The EMF of the current source is 30 V, and its internal resistance is 2 ohms.

September 25, 2021 | education

| **The EMF of the current source is 30 V, and its internal resistance is 2 ohms. Determine the load resistance if the full power that it emits, the source is 90 W.**

EMF = 30 V.

r = 2 ohms.

N = 90 W.

R -?

The current power is determined by the formula: N = I * EMF, where I is the current strength, EMF is the electromotive force of the current source.

Let’s write Ohm’s law for a complete closed circuit: I = EMF / (r + R), where r is the internal resistance of the current source, R is the external resistance.

N = I * EMF = EMF ^ 2 / (r + R).

r + R = EMF ^ 2 / N.

R = EMF ^ 2 / N – r.

R = (30V) ^ 2 / 90W – 2 ohms = 8 ohms.

Answer: the resistance of the external load is R = 8 ohms.

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