An electric bulb is rated 220 V and 100 W. When it is operated on 110 V, the power consumed will be:
The bulb parameters are as given below:
Power, P = 100W
Potential difference, V = 220V
Then Resistance, R = ?
This resistance of the bulb will remain constant i.e. 484
Now, when we operate this bulb on 110 V, then,
Power, P =?
Potential difference, V = 110V
And, resistance, R = 484
P = = = 25 W
Thus, the correct answer is: (d) 25 W.
Explain the following:
(a) Why is the tungsten used almost exclusively for the filament of electric lamps?
(b) Why are the conductors of electric heating devices such as bread toasters and electric irons made of an alloy rather than a pure metal ?
(c) Why is the series arrangement not used for domestic circuits?
(d) How does the resistance of a wire vary with its area of cross-section?
(e) Why are copper and aluminium wires usually employed for electricity transmission?