InterviewSolution
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InterviewSolution
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A sample of an ideal gas initially having internal energy `U_(1)` is allowed to expand adiabatically performing work W. Heat Q is then supplied to it, keeping the volume constant at its new value, until the pressure raised to its original value. The internal energy is then `U_(3)` (see figure). find the increase in internal energy `(U_(3) - U_(1))`? A. `Q + W`B. `Q - W`C. `gamma W - Q`D. `Q - gamma W` |
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Answer» Correct Answer - B Process `1 rarr 2 ` is adiabatic `Q_(12) = DeltaU_(12) + W_(12) = gt 0 = (U_2-U_1) + W` `U_2 - U_1 = -W` Process `2 rarr 3` is isochoric `Q_(23) = Delta U_(23) + W_(23) implies Q = U_(3)-U_(2)` `W_(23) = 0 :. V = consta nt` `implies U_(3) -U_(2) = Q` Now `(U_(3)-U_(2)) + (U_(2)-U_(1)) = U_(3)-U_(1)` `implies Q _(-W) = U_(3) - U_(1)` `implies U_3 = Q +U_(1) -W implies U_(3) -U_(1) = Q-W`. |
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