A bulb is made using two filaments. A switch selects whether the filaments are used individually or in parallel. When used with a 15 V battery, the bulb can be operated at 5 W, 10 W or 15 W. What should be the resistances of the filaments ?
The various resistances of the bulbs =v2p
Resistances are
(15)25,(15)210,(15)215=45,22.5,15
Since two resistances when used in parallel have resistances less than both. The resistances are 45 & 22.5