L11 - Exercises

# L11 - Exercises - PH2103 Thermal Physics Mid-term exam...

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PH2103 Thermal Physics Mid-term exam Monday 21 st September Hall C - Block N2-B2C-12 10:30-12:30 1h exam - starts at 11:00 Open book exam (everything but electronic devices)

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PH2103 Thermal Physics Lecture 11: Exercises Massimo Pia Ciamarra [email protected] SPMS-PAP-03-14 Discussion Forum
Ex 1 n = 2 moles of a monoatomic ideal gas undergo a reversible thermodynamic transformation. In this transformation, the pressure varies as P = bT 2 , and the temperature varies from T i to T f . b = 2 J m -3 K -2 ; T i = 400 K; T f = 300 K (a) calculate the W work done by the gas (b) the heat exchanged

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Ex 1 n = 2 moles of a monoatomic ideal gas undergo a reversible thermodynamic transformation. In this transformation, the pressure varies as P = bT 2 , and the temperature varies from T i to T f . b = 2 J m -3 K -2 ; T i = 400 K; T f = 300 K (a) calculate the W work done by the gas W gas =− W on = V i V f P ( V ) dV W gas =− W on = V i V f P ( V ) dV =− nR ( T f T i ) We need to determine P(V), V f and V i PV = nRT ; P = bT 2 →( PV ) 2 =( nR ) 2 T 2 →( PV ) 2 =( nR ) 2 P b P ( V )= ( nR ) 2 bV 2 V f = nRT f P = nRT f bT f 2 = nR bT f V i = nR bT i
Ex 1 n = 2 moles of a monoatomic ideal gas undergo a reversible thermodynamic transformation. In this transformation, the pressure varies as P = bT 2 , and the temperature varies from T i to T f . b = 2 J m -3 K -2 ; T i = 400 K; T f = 300 K; R = 8.314 J/mole (a) calculate the W work done by the gas W gas =− W on = V i V f P ( V ) dV W gas =− W on = V i V f P ( V ) dV =− nR ( T f T i )= 1663 J We need to determine P(V), V f and V i PV = nRT ; P = bT 2 →( PV ) 2 =( nR ) 2 T 2 →( PV ) 2 =( nR ) 2 P b P ( V )= ( nR ) 2 bV 2 V f = nRT f P = nRT f bT f 2 = nR bT f V i = nR bT i

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Ex 1 W gas =− W on = V i V f P ( V ) dV = T i T f P ( T ) dV dT dT PV = nRT V = nRT P = nRT bT 2 dV dT = nR bT 2 = nR P We can also make a change of variable (a) calculate the W work done by the gas W gas =− W on = T i T f P ( nR P ) dT = T i T f P =− nR T i T f dT =− nR ( T f T i )
Ex 1 n = 2 moles of a monoatomic ideal gas undergo a reversible thermodynamic transformation. In this transformation, the pressure varies as P = bT 2 , and the temperature varies from T i to T f .

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• Fall '15

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