Question

A rigid container with thermally insulated walls contains a coil of resistance 100 $\Omega$, carrying current 1 A. Change in internal energy after 5 min will be

• A. Zero
• B. 10 kJ
• C. 20 kJ
• D. 30 kJ

Answer 1

Answer: (D)

30 kJ

Answer 2

W = 0. Therefore, from first law of thermodynamics,
$\, \, \, \, \, \, \Delta U = \Delta Q = i^2Rt$
$\, \, \, \, \, \, \, \, \, \, = (I)^2 (100) (5 \times 60)J = 30kJ$
$\therefore$ Correct answer is (d).