Question

Two ( non-physics) students,A and B living in neighboring hostel rooms, decide economies by connecting their bulbs in series. They agreed that each would install a 100 W bulb in their own rooms and that they would pay equal shares of the electricity bill. However,both decide to try to get better lighting at the other's expense:A installed a 200 W bulb and B installed a 50 W bulb which student is more likely to fail the end-of-term examinations?

Answer 1

We have two bulbs, 100 W and 50 W - I assume the voltage is 230 V 50 Hz single phase A.C. the standard supply

When P is 100W, Current(I) is higher

but when P = 50W, current is lower (remember that V is constant)

then use V = IR, when current is high, resistance is low

Hence 50 W bulb has a higher resistance than 100W bulb