The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated 100 W and 200 V is connected across 220 V power supply. If the voltage drops by 10%, then the power of the lamp will be
a)
90 W
b)
81 W
c)
Between 90 and 100 W
d)
Between 81 and 90 W
The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated 100 W and 200 V is connected across 220 V power supply. If the voltage drops by 10%, then the power of the lamp will be
a)
90 W
b)
81 W
c)
Between 90 and 100 W
d)
Between 81 and 90 W
Question ID - 151198 | SaraNextGen Top Answer
The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated 100 W and 200 V is connected across 220 V power supply. If the voltage drops by 10%, then the power of the lamp will be
a)
90 W
b)
81 W
c)
Between 90 and 100 W
d)
Between 81 and 90 W
|
The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated 100 W and 200 V is connected across 220 V power supply. If the voltage drops by 10%, then the power of the lamp will be |
|||
|
a) |
90 W |
b) |
81 W |
|
c) |
Between 90 and 100 W |
d) |
Between 81 and 90 W |
|
(d) Let the resistance of the lamp filament be
Here, |
Then 
When the voltage drops, expected power is
will be less than 
because now the rise in temperature will be less. Therefore, 
is more than 
But it will not be 90% of earlier value, because fall in temperature is small. Hence, option (d) is correct.