EMF of the 2V battery. With a current in the 2A circuit, the voltage at the battery terminals is 1.8V

EMF of the 2V battery. With a current in the 2A circuit, the voltage at the battery terminals is 1.8V, find the internal resistance in working condition.

According to Ohm’s law, we determine the external resistance of the circuit.

I = U / R.

R = U / I = 1.8 / 2 = 0.9 Ohm.

Let’s apply Ohm’s law to the complete circuit.

I = E / (R + r), where E is the EMF of the circuit, R is the external resistance of the circuit, r is the internal resistance of the power source.

(R + r) = E / I.

r = (E / I) – R = (2/2) – 0.9 = 1 – 0.9 = 0.1 ohm.

Answer: The internal resistance of the source is 0.1 ohm.