1
GATE ME 2008
MCQ (Single Correct Answer)
+2
-0.6
In a steady state steady flow process taking place in a device with a single inlet and a single outlet, the work done per unit mass flow rate is given by $$W = - \int_{inlet}^{outlet} {vdp} ,$$ where $$v$$ is the specific volume and $$P$$ is the pressure. The expression for $$'W'$$ given above
A
is valid only if the process is both reversible and adiabatic
B
is valid only if the process is both reversible and isothermal
C
is valid for any reversible
D
is incorrect, it must be $$W = \int_{inlet}^{outlet} {pdv} $$
2
GATE ME 2006
MCQ (Single Correct Answer)
+2
-0.6
A $$100$$ $$W$$ electric bulb was switched on in a $$2.5\,m \times 3m \times 3m$$ size thermally insulated room having a temperature of $${20^ \circ }C$$. The room temperature at the end of $$24$$ hours will be
A
$${321^ \circ }C$$
B
$${341^ \circ }C$$
C
$${450^ \circ }C$$
D
$${470^ \circ }C$$
3
GATE ME 2005
MCQ (Single Correct Answer)
+2
-0.6
Nitrogen at an initial state of $$10$$ bar, $$1{m^3}$$ and $$300$$ $$K$$ is expanded isothermally to a final volume of $$2{m^3}$$. The $$p$$-$$v$$-$$T$$ relation is $$\left( {p + {a \over {{v^2}}}} \right)v = RT,$$ where $$a>0.$$ The final pressure
A
will be slightly less than $$5$$ bar
B
will be slightly more than $$5$$ bar
C
will be exactly $$5$$ bar
D
cannot be ascertained in the absence of the value of $$a.$$
4
GATE ME 1993
Subjective
+2
-0
A vertical cylinder with a freely floating piston contains $$0.1$$ $$kg$$ air at $$1.2$$ bar and a small electrical resistor. The resistor is wired to an external $$12$$ Volt battery. When a current of $$1.5$$ amps is passed through the resistor for $$90$$ $$secs,$$ the piston sweeps a volume of $$0.01$$ $${m^3}.$$ Assume $$(i)$$ piston and the cylinder are insulated and $$(ii)$$ air behaves as a ideal gas with $${C_v} = 700\,\,J/kg\,K.$$
Find the rise in temperature of air. GATE ME 1993 Thermodynamics - Calculation of Work and Heat Question 9 English
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