Q. A railway compartment is lit up by thirteen lamps each taking 2.1 A at 15 V. The heat generated per second in each lamp will be
A) 4.35 cal
B) 5.73 cal
C) 7.5 cal
D) 2.5 cal
Explanation
(c) From Joule’s law, for a current carrying conductor at a definite temperature the rate of production of heat is given by
$H = Vit$
Where $i$ is current, $V$ the potential difference and $t$ the time.
Given, $V = 1.5\ volt,\ i = 2.1\ A,\ t = 1s$
$\therefore H = 15 \times 2.1 \times 1 = 31.5\ J$
Also, $1\ cal = 4.2\ J$
$\therefore H = \frac{31.5}{4.2} = 7.5\ cal$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.