Q. 100 g of water is heated from$30℃\ to\ 50℃.$Ignoring the slight expansion of the water, the change in its internal energy is (Specific heat of water is 4184 J/kg/K)
A) 8.4 kJ
B) 84 kJ
C) 2.1 kJ
D) 4.2 kJ
Explanation
(a) As work done=0
$\mathrm{\Delta}U\ = mc\mathrm{\Delta}T$
$\ \ \ \ \ \ \ \ = 100 \times 10^{- 3} \times 4184 \times (50 - 30)$
=84 kJ
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.