Q. An immersion heater is rated 418 W. It should heat a litre of water from 10$℃\ $to 30$℃$ in nearly
A) 44 s
B) 100 s
C) 200 s
D) 400 s
Explanation
(c) $418t = 1 \times 4180 \times 20\ or\ t = 200\ s$
Note that in this case, $C = 418\ J/kg^{- 1}\lbrack ℃^{- 1}\rbrack$
$\ J = 4.18\ J\ cal^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.