The strength of the electric current in the battery circuit, the EMF of which is 30 V, the current strength is 3 A.

The strength of the electric current in the battery circuit, the EMF of which is 30 V, the current strength is 3 A. The internal resistance of the battery is 1 Ohm. Find the resistance of the external circuit.

To find the required resistance of the external circuit, we apply the formula: I = ε / (R + r), whence R = ε / I – r.

Values of variables: ε – EMF in the battery circuit (ε = 30 V); I is the current in the created circuit (I = 3 A); r is the internal resistance of the battery (r = 1 ohm).

Let’s calculate: R = ε / I – r = 30/3 – 1 = 9 Ohm.

Answer: The resistance of the external circuit connected to the battery circuit is 9 ohms.