(a)

P: 0.3 A
Q: 0.4 A

(b)

Conductor Q is ohmic,, because the voltage of the circuit increases linearly with the current flowing through the circuit so that its resistance (gradient of the V - I graph) is constant AND V = 0 when I = 0.

(c)

Resistance of Q
= Value of V / Value of I
= 2.0 V / 0.4 A
= 5.0 ohm

(For V - I graphs, we read off V and I values and then divide each other to obtain the resistance, and NOT the usual way of drawing tangent to a curve which is usually the case for other scenarios involving gradients).

(d)

Resistance = resistivity * length of wire / cross sectional area of wire

Similar material = same resisvitity
Double the length = resistance becomes twice
Four times the area = resistance becomes times 1/4

Overall, Q2 has a resistance half of Q1, so the gradient of Q2 is half of the gradient of Q1

The graph of Q2 must pass (0, 0) and (1, 0.4) on the V - I axis.

Overall, Q3 has a resistance twice of Q1, so the gradient of Q3 is twice the gradient of Q1.

The graph of Q3 must pass (0, 0) and (2, 0.2) on the V - I axis.