Question

A circuit with a resistance of `6 Omega` has a fuse that melts at `8 A`. Can a voltage of `12 V` be applied to the circuit without blowing the fuse?

Answer 1

No, you would need a voltage of at least `48V`.

Explanation:

We are interested here in the current, because if the current comes above a certain point the circuit will blow. The equation for current is

`I=V/R`.

We know that `R=6Omega`, and that `12V` are being sent through the circuit, so

`I=(12V)/(6Omega)=2A`

A current of `8A` will blow the circuit, so quite clearly a current of `2A` when the voltage is `12V` won't.

When current is at `8A` or above, then voltage must be

`V>=8A*6Omega`
`V>=48V`

for the circuit to break.