With a short circuit of the battery terminals, the current in the circuit is 14 A. When an electric lamp is connected

| September 2, 2021 | education

With a short circuit of the battery terminals, the current in the circuit is 14 A. When an electric lamp is connected to the battery terminals with electrical resistances of 6 Ohms, the current in the circuit is 2 A. According to the results of these experiments, determine the EMF of the battery.

Izam = 14 A.

R = 6 ohms.

I = 2 A.

EMF -?

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

A short circuit condition is the absence of an external resistance R = 0.

For a short circuit, Ohm’s law will have the form: Icor = EMF / r.

I * (R + r) = Icor * r.

I * R + I * r = Icor * r.

I * R = Icor * r – I * r.

r = I * R / (Icor – I).

r = 2 A * 6 Ohm / (14 A – 2 A) = 1 Ohm.

EMF = Icor * r.

EMF = 14 A * 1 Ohm = 14 V.

Answer: EMF = 14 V.



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