### Video Transcript

The diagram shows a circuit
consisting of a light bulb connected to a cell. The potential difference across the
bulb is nine volts, and the current through it is four amps. How much is the power of the light
bulb?

Taking a look at this circuit, we
see that indeed this bulb is set up in series with a cell. With the circuit set up like this,
the bulb will be on shining light and we want to know just how much power it’s using
up as it does so. We’re told the potential difference
across the bulb as well as the current through it. And we can recall the relationship
for potential difference current and power. That equation tells us that power
𝑝 is equal to current times voltage.

Applying this to our scenario, we
can substitute in the given values of current four amps and voltage nine volts. Then when we go and multiply these
quantities together, we find the result of 36 watts. That’s the power of the light bulb,
likely given off both in the form of light as well as heat energy.