Electrical Circuit
Electricity and Magnetism

Shifting energy from a battery

Physics Narrative for 11-14 Supporting Physics Teaching

A chemical store, depleted

Find out more about describing the energy shifted from the chemical store.

We said: Energy is shifted by the charged particles as they pass through the battery. What does this mean? To answer the question it is helpful to return to the detailed explanation of how electric circuits work introduced in episode 01.

All of the charged particles (imagine positively charged particles) in the circuit experience a force to move them round from the positive to the negative terminal of the battery. When each charge arrives at the negative terminal, energy must be shifted as it moves across the battery from the negative plate to the positive plate (against the repelling force of the positive plate). The energy required comes from the chemical store of the battery, which is emptied by the electrical working pathway.

An example. For a 12 volt battery with a current of 0.25 ampere, the power switched is 3 watt The result of this accumulated action is that, over one second:

  • 0.25 coulomb passes through the bulb (0.25 ampere  ×  1 second.)
  • 3 joule is shifted (3 watt  ×  1 second.)

So 3 joule of energy is shifted from the chemical store for each coulomb of charge making the trip from negative to positive plate.

What is in the rest of the circuit determines the stores of energy that are filled as a result of the chemical store being emptied. This ability to shift energy is why electric circuits are so useful.

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