**electric heaters**), light (

**light bulbs and neon tubes**), or motion, i.e. kinetic energy (

**power tools**).

From the definition of potential difference, **V**, we have **V = W/Q**, where **W** is the work done by charge **Q**. Hence, **W = VQ**.

Current is the flow of charge, so that in time t, the amount of charge moving through the conductor will be **Q = It**.

Therefore, **W = VIt** gives the work done in time **t**, by a current I, flowing through a conductor across which the potential difference is **V**. This may be written in two other ways by substituting from Ohm's Law:

where **R** is the resistance of the conductor.

## Electric power:

Remember that power is defined as the rate at which work is done:

By substituting from **W = VIt**, we obtain the formula for the power dissipated in an electric circuit, as follows:

This formula gives the power which is dissipated when a current **I** moves through a conductor across which there is a potential difference **V**.

From Ohm's law we may also write

The unit of power is the **WATT, W** which is equivalent to one joule per second, J.s^{-1}.

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