EXERCISES

Two lamps, one rated $100 \mathrm{W}$ at $220 \mathrm{V}$, and the other $60 \mathrm{W}$ at $220 \mathrm{V}$, are connected in parallel to the electric mains supply. What current is drawn from the line if the supply voltage is $220 \mathrm{V}$?

Which uses more energy, a $250 \mathrm{W}$  TV set in $1 \mathrm{hr}$, or a $1200 \mathrm{W}$  toaster in $10 \mathrm{minutes}$?

An electric heater of resistance $8 \Omega$ draws $15 \mathrm{A}$ from the service mains $2 \mathrm{hours}$. Calculate the rate at which heat is developed in the heater.

Why is the tungsten used almost exclusively for filament of electric lamps?

Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal? 

Why is the series arrangement is not used for domestic circuits? 

How does the resistance of a wire vary with its area of cross-section? 

Why are copper and aluminium wires usually employed for electricity transmission?