## Electrical working

Physics Narrative for 14-16

#### The energy shifted each second is the power in the pathway

The energy shifted every second in this circuit depends on both the current and the potential difference. In this simple circuit there is only one value for the current and one value for the potential difference. In more complex circuits you need to be more careful when identifying and describing the currents and potential differences. This was covered in episode 01. In this episode you will learn how to combine these quantities to find out how much energy is shifted each second by different circuit elements.

The calculation done for each pathway shows the power: the rate at which stores of energy are emptied or filled. Finding the power in the electrical pathway is very simple – you multiply the potential difference by the current.

(Think about fundamentals again, from the SPT: Electric circuits topic. The current is the charge each second, and the potential difference is the energy for each charge. In this episode we approach the same end point by thinking about power.)

Arranging such a circuit to shift energy at a particular rate is then simply a question of choosing the potential difference of the cell and the resistance of the lamp or resistor. These jointly determine the current, as shown in episode 01. The current and the potential difference then together set the power.

Energy is shifted to and from stores by the action of the electrical pathway for as long as the circuit is connected. The rate at which this happens is the power, measured in watts. This power is set by the potential difference and the current.