Question

If a current of `4 A` passing through a circuit generates `42 W` of power, what is the resistance of the circuit?

Answer 1

`approx2.6Omega`

Explanation:

Power is current times voltage,

`P=IV`

Substituting in the power is `42W` and current is `4A` from the question,

`42=4*V`
`V=10.5`

A second equation tells us that voltage is current times resistance, so

`V=IR`.

Putting in the values of `V=10.5V` and `I=4A` and rearranging to make `R` the subject,

`R=10.5/4=2.625Omegaapprox2.6Omega`

You could put the two equations together and say that

`R=P/I^2`

and simply solve straightaway.