A transformer for charging a power tool steps the line voltage down to 2.9 V. The output current of this transformer is 240 mA. If the transformer is ideal (100% efficient), what is the input current?

Question

Quizplus · Accepted Answer

For an ideal transformer, the power input equals the power output. Therefore, V_in * I_in = V_out * I_out. Given V_out = 2.9 V and I_out = 240 mA, and assuming V_in is the line voltage (typically 120 V in the US), we solve for I_in: I_in = (V_out * I_out) / V_in = (2.9 V * 240 mA) / 120 V = 5.8 mA.

A Transformer for Charging a Power Tool Steps the Line