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In a certain process, 400 J of heat energy is supplied to a system, and at the same time, 150 J of work is done by the system. The increase in internal energy of the system is

Correct answer: C. 250 J

  • A. 150 J
  • B. 300 J
  • C. 250 J
  • D. 500 J

Explanation

According to the first law of thermodynamics, ΔU = Q - W. Heat is supplied, so Q = +400 J, and work is done by the system, so W = +150 J. Therefore, the change in internal energy is ΔU = 400 J - 150 J = 250 J.

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About First Law of Thermodynamics

The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.

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