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AP EAMCET · PHYSICS · Thermodynamics

A gas does \(4.5 \mathrm{~J}\) of external work during adiabatic expansion. If its temperature falls by \(2 \mathrm{~K}\), then its internal energy will be

  1. A increased by \(4.5 \mathrm{~J}\)
  2. B decreased by \(4.5 \mathrm{~J}\)
  3. C decreased by \(2.25 \mathrm{~J}\)
  4. D increased by \(9.0 \mathrm{~J}\)
Verified Solution

Answer & Solution

Correct Answer

(B) decreased by \(4.5 \mathrm{~J}\)

Step-by-step Solution

Detailed explanation

From first law of thermodynamics, \(\begin{aligned} & d Q=d U+d W \\ & \Rightarrow \quad d U=-d W \quad \text { [In adiabatic process } d Q=0 \text { ] } \\ & d U=-4.5 \mathrm{~J} \end{aligned}\) As, the temperature falls so internal energy will decrease by \(4.5 \mathrm{~J}\)