In the circuit shown, lamps L₁ and L₂, are identical. The sliding contact at O moved towards Q, then which of the statements about the effect on the brightness in L₂ is correct?

1. Initially it has no light, then its brightness increases gradually and becomes equal to that of L₁
2. Initially it is same as that of L₁, and finally become half as that of L₁
3. Initially it is half as that of L₁ and finally becomes equal to that of L₁.
4. Initially it is half as that of L₁ and finally becomes zero.

The force of 20 N is applied at distance of 40 cm from the axis. The moment of force is

1. 8 N-m
2. 0.4 N-m
3. 8.5 N-m
4. 20 N-m

When the displacement is along the opposite direction of the force, then the work is said to be

1. zero
2. negative
3. positive
4. infinite