Question

A charge of `12 C` passes through a circuit every `4 s`. If the circuit can generate `8 W` of power, what is the circuit's resistance?

Answer 1

I got: `0.9Omega`

Explanation:

Here we have a current `I` of charge passing through the circuit in a given time, or:
`I="charge"/"time"=12/4=3A`
The power is energy delivered by our charges (passing in the circuit) at each second.
We can write power in general as:
`P=VI` But here we take advantage of Ohm's Law, `V=RI`, to rearrange our expression of Power to include resistance as:
`P=I^2R`
so that:
`R=P/I^2=8/9=0.89=0.9Omega`