The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated 100, W, 220, V is connected across 220,

Q: The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated $100\, W, 220\, V$ is connected across $220\, V$ power supply. If the voltage drops by $10\%$ then the power of lamp will be

d (d) Let the resistance of the lamp filament be $R$. Then $100 = \frac{{{{(220)}^2}}}{R}$. When then voltage drops, expected power is $P = \frac{{{{(220 \times 0.9)}^2}}}{{R'}}$. Here $R'$ will be less than $R$, because now the rise in temperature will be less. Therefore $P$ is more than $\frac{{{{(220 \times 0.9)}^2}}}{R} = 81W$ But it will not be $90\%$ of earlier value, because fall in temperature is small. Hence $(d)$ is correct.

SECTION - A [PHYSICS MCQ]

GSEB - English Medium

The resistance of the filament of a lamp increases with the increase in temperature. A lamp rated $100\, W, 220\, V$ is connected across $220\, V$ power supply. If the voltage drops by $10\%$ then the power of lamp will be

A$90\, W$
B$81\, W$
CBetween $90\, W$ and $100\, W$
DBetween $81\, W$ and $90\, W$

Medium

STD 11 Science
JEE
STD 12 - 3. current electricity
Physics

Download our app
and get started for free

Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*

Download App

Similar Questions

1
Current of $4.8\,A$ is flowing through a conductor. The number of electrons per second will be
View Solution
2
Fig. shows rough sketch of meter bridge. $(G)$ deflects zero at length $l\, cm$. Now $R_1$ and $R_2$ are interchanged then balancing length increases by $25\, cm$. Find $R_1/R_2$
View Solution
3
If power dissipated in the $9 \,\Omega$ resistor in the circuit shown is $36\,W$, the potential difference across the $2 \,\Omega$ resistor is .......... $V$
View Solution
4
There are a large number of cells available, each marked $(6 \,V , 0.5 \,\Omega)$ to be used to supply current to a device of resistance $0.75 \,\Omega$, requiring $24 \,A$ current. How should the cells be arranged, so that power is transmitted to the load using minimum number of cells?
View Solution
5
Suppose a current carrying wire has a cross-sectional area that, gradually become smaller along the wire, has the shape of a very long cone as shown in figure. Choose the correct statement
View Solution
6
Consider the circuit shown in fig. The current through the $10\,\Omega $ resistor when switch $'s'$ is $(a)$ open $(b)$ closed.
View Solution
7
If $n, e, \tau$ and $m$ are representing electron density, charge, relaxation time and mass of an electron respectively, then the resistance of a wire of length / and cross-sectional area $A$ is given by
View Solution
8
Three resistors each of $4\,\Omega $ are connected together to form a network. The equivalent resistance of the network cannot be ............ $\Omega$
View Solution
9
Assertion : Ohm's law is applicable for all conducting elements.

Reason : Ohm's law is a fundamental law
View Solution
10
A hot electric iron has a resistance of $80\,\Omega $ and is used on a $200\, V$ source. The electrical energy spent, if it is used for two hours, will be ........... $Wh$
View Solution

Download our appand get started for free

Similar Questions

Download our app
and get started for free