Question

If a current of `8 A` passing through a circuit generates `14 W` of power, what is the resistance of the circuit?

Answer 1

The resistance in the circuit will be 0.22 `Omega`

Explanation:

I would combine two laws I have memorised here: Ohm's Law,

`V = IR`

and the Power Law

`P = VI`

I have a current, `I`, of `"8 A"` (ampere) and a power, `P`, of `"14 W"` (watt). I have been asked for a resistance, `R` `Omega` (ohm).

So I want a formula that includes only those three things. If I want to get rid of the `V` in the Power Law, I can replace it with what Ohm's Law says is equal to `V= IR`. So

`P = (IR) * I = I^2 * R`

I need to rearrange to make `R` the subject, so I divide both sides by `I^2` and swap the sides:

`R = P/(I^2) = 14/(8^2) = 14/64 = 0.22 color(white)(a)Omega` (rounded to two decimal places).