Which of the following materials are the good conductors of electricity?

Calculate the effective resistance across AB.

The diagram above shows a circuit with the key k open. Calculate the resistance of the circuit when the key k is open and calculate the current drawn from the cell when the key k is open.

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 $220 \mathrm{V}$?

What is a conductor of electricity? Give two examples.

Conductors and insulators are equally important for us. Give reasons.