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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Laws of Thermodynamics

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Laws of Thermodynamics

Determine the heat absorbed by a system undergoing the cyclic...

Determine the heat absorbed by a system undergoing the cyclic process depicted in the figure.
Determine the heat absorbed by a system undergoing the cyclic process depicted in the figure.

Options

  1. A10.0 J10.0\text{ J}
  2. B3.14 J3.14\text{ J}
  3. C31.4 J31.4\text{ J}
  4. D314 J314\text{ J}

Correct answer

C. 31.4 J31.4\text{ J}

Step-by-step solution

For a cyclic process, the change in internal energy is zero (ΔU=0\Delta U = 0).

According to the first law of thermodynamics, the heat absorbed is equal to the work done:

Q=WQ = W

The magnitude of work done in a cyclic process is given by the area enclosed by the cycle on the indicator diagram.

From the given V−pV-p graph, the semi-axes of the closed curve are:

rp=300−1002=100 kPa=105 Par_p = \dfrac{300 - 100}{2} = 100 \text{ kPa} = 10^5 \text{ Pa}

rV=300−1002=100 cc=100×10−6 m3=10−4 m3r_V = \dfrac{300 - 100}{2} = 100 \text{ cc} = 100 \times 10^{-6} \text{ m}^3 = 10^{-4} \text{ m}^3

The area of the cycle is:

Area=π×rp×rV\text{Area} = \pi \times r_p \times r_V

Area=π×(105 Pa)×(10−4 m3)\text{Area} = \pi \times (10^5 \text{ Pa}) \times (10^{-4} \text{ m}^3)

Area=10π J\text{Area} = 10\pi \text{ J}

Using π≈3.14\pi \approx 3.14, we get:

∣W∣=10×3.14=31.4 J|W| = 10 \times 3.14 = 31.4 \text{ J}

Therefore, the magnitude of heat absorbed is 31.4 J31.4 \text{ J}.
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