In an electrical circuit, a battery is connected to pass 20C of charge through it in a certain given time. The potential difference between two plates of the battery is maintained at 15V. The workdone by the battery is __________J.

Solution

Physics sir · 3 steps

Voltage is work done per unit charge, so multiply the charge by the voltage and you have the work.

1. What voltage means. A potential difference of 15 V means the battery does 15 J of work on every coulomb of charge it pushes through. So the work done is the charge multiplied by the potential difference.

   W = qV

2. Put in numbers. W = 20 C × 15 V = 300 J. The time is not needed, because the work depends only on how much charge moves and the voltage it moves through.
3. So. The work done by the battery is 300 J.

The common slip: 0.75. Dividing instead of multiplying, W = V/q = 15/20, gives 0.75. One volt is one joule per coulomb, so multiply by the charge.

The idea to keep. Work done by a battery is W = qV. If time is given, it only matters when the question asks for power or current, not for the total work.

Answer from the NTA final answer key. Solution by PrepWiser.