Q. A heater coil is cut into two parts of equal length and one of them is used in the heater. The ratio of the heat produced by this half coil to that by the original coil is
A) 2 :1
B) 1 :2
C) 1 :4
D) 4 :1
Explanation
(a) $P = \frac{V^{2}}{R} \Rightarrow P \propto \frac{1}{R}\ $and$\ R \propto l$
$\therefore P \propto \frac{1}{l} \Rightarrow \frac{P_{1}}{P_{2}} = \frac{l_{2}}{l_{1}} = \frac{2}{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.