Power in Circuits

Power - the rate at which energy is "consumed"

P = E / t

Energy (in joules) per time (in seconds)
- new unit (joule/sec) is called a watt (W)

For electricity:

P = E/t
But recall that V = E/q

So....

P = V q / t

And since q/t = I

P = V I

Or

P = I^2 R

In other words, the power of a light bulb depends on its resistance.

For identical light bulbs in a circuit, only the current will matter when trying to determine brightness.

Consider:

- 2 bulbs in series vs 2 bulbs in parallel. Which are brighter?

- 3 bulbs in series vs 2 in series

- 2 bulbs in parallel, which are then in series with another bulb