Question

'A fuse is rated $8A$'. Can it be used with an electrical appliance of rating $5kW$, $200V$?

Answer 1

A fuse of current rating $8A$ will allow the maximum current of $8A$ to pass through it without damaging it.
Given, the rating of the electrical appliance
Power, $P=5kW$ and
Voltage $V=200Volts$
Maximum current that can flow through the appliance,
$I_{cr.}=\frac{Power}{Voltage}$
$I_{cr.}=\frac{5000W}{2000V}$
$I_{cr.}=25A$
$I_{cr.}$ $\left(25A\right)$ is greater than $I_{max}$ $\left(8A\right)$. Hence, the $8A$ current rating fuse cannot be used with the given electric appliance.