Multiple choice

The contents of a well-insulated tank are heated by a resistor of 23 W in which 10 A current is flowing. Consider the tank along with its contents as a thermodynamic system. The work done by the system and the heat transfer tothe system are positive. The rates of heat (Q), work (W) and change in internal energy (DU) during the process (in kW) are

  1. Q = 0, W = −23, $\triangle$U = +23
  2. Q = +23, W = 0, $\triangle$U = +23
  3. Q = −23, W = 0, $\triangle$U = −23
  4. Q = 0, W = +23, $\triangle$U = −23
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Applying 1st law of thermodynamics, Q - W = U, where Q is the heat flow rate into the system, W is the work done rate by the system and U is the rate of internal energy change of the system. W = 0 as volume of the system is not changing. Thus, we get Q = U. But, Q = 23 W Thus, U = 23W as well. Hence, option 2 is correct  

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