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A gas does 4.5 J of external work during...

A gas does 4.5 J of external work during adiabatic expansion. If its temperature falls by 2 K, then its internal energy will be

A

Increased by `4.5J`

B

Decreased by `4.5 J`

C

Decreased by `2.25 J`

D

Increased by `9.0 J`

Text Solution

Verified by Experts

The correct Answer is:
B
`dQ = dU + dW`
`dQ = 0` (`because` adiabatic expansion)
`implies 0 = dU +dW`
`implies 0 = dU + 4.5`
`therefore` `dU = -4.5 J`
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