Question

a filament of a 240v,100w electric lamp heat up from room temperature to its operating temperature as it heat up ,its resistance increases by a factor of 16 what is the resistance of lamp at room temperature

Answer 1

Answer:

36 Ohm

Step by step explanation:

We are given the voltage of the lamp, which is 240 V and the power, which is 100 W. It is required to find the resistance of the lamp at room temperature.

First of all, we find the resistance of the lamp when it is heated up as follows:

$P=\frac{V^2}{R}\\100=\frac{(240)^2}{R}\\R=576\:Ohm$

It is also given that the resistance of the lamp increases by a factor of 16 when it is heated up. Therefore, to find the resistance of the lamp at room temperature, we need to divide the resistance we just obtained by 16.

Therefore, at room temperature the resistance is: $R=\frac{576}{16}=36\:Ohm$