The electrical resistivity of three materials A, B and C at $20^{\circ}C$ is given below:

Material | Resistivity (Ω m)

A | $10^{17}$

B | $44 \times 10^{-6}$

C | $1.62 \times 10^{-8}$

(i) Classify these materials as conductor, alloy and insulator.

(ii) Give one example of each of these materials and state one use of each material in the design of an electrical appliance say an electric stove or an electric iron.

(i) Material A is an insulator as its resistivity is of the order of $10^{17} Ω m$. Material B is an alloy as its resistivity is of the order of $10^{-6} Ω m$. Material C is a conductor as its resistivity is of the order of $10^{-8} Ω m$.

(ii) Material A (insulator): One example is wood. It is used for making handles of electrical appliances like an electric stove or an electric iron as it does not allow current to pass through it.

Material B (alloy): One example is Manganin. It is used for making heating elements like heating coil of an electric stove or an electric iron as it has high resistivity and does not oxidise readily at high temperatures.

Material C (conductor): One example is copper. It is used for making connecting wires of electrical appliances like an electric stove or an electric iron as it has low resistivity and is a good conductor of electricity.