First slide

Thermal effect of current

Question

If the length of the filament of a heater is reduced by 10% by cutting its length, the power of the heater will be nearly, (if constant voltage is maintained across the heater)

Moderate

A

Increase by about 9%
B

Increase by about 11%
C

Increase by about 19%
D

Decrease by about 10%

Solution

Power of a heater is given as
$\begin{array}{l} P = \frac{V^{2}}{R} \\ \Rightarrow P \propto \frac{1}{R} r e s i s \tan c e o f a w i r e i s d i r e c t l y p r o p o t i o n a l t o i t s l e n g t h . \\ \Rightarrow \frac{P_{2}}{P_{1}} = \frac{R_{1}}{R_{2}} = \frac{l_{1}}{l_{2}} \\ \Rightarrow P_{2} = (\frac{l_{1}}{l_{2}}) P_{1} = (\frac{l}{0.9 l}) P_{1} = 1.11 P_{1} \end{array}$
So, power will be increased by 11%.

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App