What property of the filament wire accounts for this difference?

The electrical resistivities of four materials P, Q, R and S are given below :

P - 6.84 × 10^-8 Ω m

Q - 1.70 × 10^-8 Ω m

R - 1.0 × 10¹⁵ Ω m

S - 11.0 × 10^-7 Ω m

Which material will you use for making:

(a) heating element of electric iron

(b) connecting wires of electric iron

(c) covering of connecting wires? Give reason for your choice in each case.

How does the wire in the filament of a light bulb behave differently to the other wires in the circuit when the current flows ?

Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for your answer.

An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at 'minimum heating' it consumes a power of 360 W but at 'maximum heating' it takes a power of 840 W. Calculate the current and resistance in each case.