The given rods will attract each other when:

1. A and C are connected to positive terminal of the battery.
2. B and C are connected to the positive terminal of the battery.
3. A and D are connected to the positive terminal of the battery.
4. A and D are connected to the negative terminal of the battery.

Which of the following equations are correctly balanced?

$\bold{A.} \quad \phantom{X}^{q-1}${p-5}X \longrightarrow \phantom{X}^{q-5}{p-3}Y + \phantom{X}^{4}{2}He \\[1em] \bold{B.} \quad \phantom{X}^{q-4}{p-4}Z \longrightarrow \phantom{X}^{q-4}{p-5}X + \phantom{X}^{\phantom{1}0}{-1}e \\[1em] \bold{C.} \quad \phantom{X}^{q-1}{p-5}X \longrightarrow \phantom{X}^{q-5}{p-7}Y + \phantom{X}^{4}{2}He \\[1em] \bold{D.} \quad \phantom{X}^{q-4}{p-7}Z \longrightarrow \phantom{X}^{q-4}{p-5}X + \phantom{X}2^{\phantom{1}0}{-1}e \\[1em]

1. Only D
2. Only C
3. Both A & B
4. Both C & D

Three metals, A, B and C, are supplied with the same quantity of heat. Their masses are in the ratio 2 : 3 : 4. If they show the same rise in the temperature, then the ratio of their thermal capacities will be:

1. 1:1:1
2. 4:3:2
3. 2:3:4
4. 2:3:1

The below diagram shows different copper conductors of diameters d and 2d and lengths, which are multiples of l. The increasing order of their resistances will be:

1. A < B < C < D
2. A < C < D < B
3. A < D < C < B
4. D < A < C < B