a] What is the function of fuse in an electric circuit?
b] What would be the rating of the fuse for an electric kettle which is operated at 220V and consumes 500W power?
c] How is the SI unit of electric energy related to its commerical unit?

Explanation

a] The function of fuse in an electric circuit
The fuse in a circuit prevents over heating of the wires and appliances due to excess transfer of electric current and melts when more current passes through it. It is connected in series in domestic circuits.
b] Given,
Power: 500 watt
Voltage = 220 Volts
`I=P/V=500/220=2.27A`
Rating of fuse wire will be 2.5 or 3A
c] Commercial Unit of Energy: The SI unit joule is too small to express very large quantities of energy. Hence we use a bigger unit called kilowatt hour [kWh] to express energy. I kWh is the amount of energy consumed by an electrical gadget in one hour at the rate of 1000 J/s or IkW.