A circuit contains a 3 V battery connected in series with a 10 resistor and a 20 resistor. A switch S is connected in parallel across the 20 resistor. Determine the current through the 10 resistor when the switch S is closed.

Step-by-step solution

When the switch S is closed, it creates a short circuit across the 20 resistor. Therefore, no current flows through the 20 resistor, and the effective resistance of the circuit is only due to the 10 resistor. Effective resistance, R_ eq = 10 Voltage of the battery, V = 3 V Using Ohm's law, the current I through the circuit (and the 10 resistor) is given by: I = V R_ eq = 3 10 = 0.3 A