Q. The power of heater is 750 W at $1000℃$. What will be its power at $200℃$ if $a = 4 \times 10^{- 4}\ per℃\ $?
A) 400 W
B) 990 W
C) 250 W
D) 1500 W
Explanation
(b) $R_{1000} = V^{2}/750$ and $R_{200} = V^{2}/P;$
Now, $R_{1000} = \ R_{200}(1 + \alpha \times 800)$
So, $\ \ \frac{V^{2}}{750} = \frac{V^{2}}{P}(1 + 4 \times 10^{- 4} \times 800)$
or $\ P = 750(1 + 0.32)$ = 990 W
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.