This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Other types of Work Transfer-1”.
1. The current flow, I, in amperes, is given by I=(dC)/(dτ)
a) dC is the charge crossing a boundary
b) time taken is dτ
c) c is the charge in coulombs and t is time in seconds
d) all of the mentioned
View Answer
Explanation: This current flow is responsible for the work transfer.
2. Shaft uses which kind of motion to do work?
a) vertical motion
b) horizontal motion
c) rotational motion
d) none of the mentioned
View Answer
Explanation: When a shaft is rotated by a motor, there is work transfer into the system.
3. Shaft work is given by
a) T*ω
b) T*dθ
c) T*τ
d) none of the mentioned
View Answer
Explanation: Shaft power is the rate if doing shaft work.
4.The flow work is significant only in
a) flow process
b) open system
c) flow process & open system
d) none of the mentioned
View Answer
Explanation: Condition for the flow work.
5. Flow work is analogous to
a) shaft work
b) electrical work
c) stirring work
d) displacement work
View Answer
Explanation: Flow work is the displacement work done at the moving system boundary.
6. The infinitesimal amount of work done on changing the length of a wire with tension T from L to L+dL is
a) -FdL
b) FdL
c) -2FdL
d) 2FdL
View Answer
Explanation: It is the work done in stretching a wire.
7. Work done in stretching a wire is given by
a) -∫FdL
b) -∫EɛALdɛ
c) -AEL∫ɛdɛ
d) all of the mentioned
View Answer
Explanation: Above formulae arrive when we limit the problem within the elastic limit.
8. The surface tension acts to make the surface area of the liquid
a) maximum
b) minimum
c) zero
d) none of the mentioned
View Answer
Explanation: Characteristic of surface tension.
9. The work done per unit volume on a magnetic material is dW=-Hdl where H is
a) field strength
b) magnetization field
c) induced current
d) none of the mentioned
View Answer
Explanation: H is the field strength of the magnetic field.
10. The work is equal to the integral of the product of an intensive property.
a) true
b) false
View Answer
Explanation: Along with it, change in work is related to the extensive property.
11. A 1200 hp engine has a drive shaft rotating at 2000 RPM. Find the torque on the shaft?
a) 2214 Nm
b) 3214 Nm
c) 4214 Nm
d) 5214 Nm
View Answer
Explanation: Power, rate of work = T ω and 1 hp = 0.7355 kW = 735.5 W
ω = RPM × (2π)/(60 s) = 209.44 rad/s
T = power/ω = (1200 hp × 735.5 W/hp)/ 209.44 rad/s
= 4214 Ws = 4214 Nm.
12. A 1200 hp engine drives a car with a speed of 100 km/h. Find the force between the tires and the road?
a) 11.8 kN
b) 21.8 kN
c) 31.8 kN
d) 41.8 kN
View Answer
Explanation: Power = F V and 1 hp = 0.7355 kW = 735.5 W
velocity in m/s: V = 100 × 1000 / 3600 = 27.78 m/s
F = (1200 × 735.5)/(27.78) = 31 771 N
= 31.8 kN.
13. A work of 2.5 kJ is delivered on a rod from a piston/cylinder where the air pressure is 500 kPa. What should be the diameter of cylinder to restrict the rod motion to maximum 0.5 m?
a) 0.013 m
b) 0.113 m
c) 0.213 m
d) 0.313 m
View Answer
Explanation: W = ⌠P dV = ⌠PA dx = PA ∆x = P(π/4)(D^2)∆x
Putting the values in above equation we get
D = 0.113 m.
14. A force of 1.2 kN moves a car with 60 km/h up a hill. Find the power?
a) 20 kW
b) 30 kW
c) 40 kW
d) 50 kW
View Answer
Explanation: Power = F V = 1.2 kN × 60 (km/h)
= ( 1.2 × 10^3 × 60 )*(1000/3600)
= 20 000 W = 20 kW.
15. When a battery(12 V) is charged with 6 amp for 3 hours how much energy is delivered?
a) 477.6 kJ
b) 577.6 kJ
c) 677.6 kJ
d) 777.6 kJ
View Answer
Explanation: W = ⌠(power)dt = V i ∆t
= 12 V × 6 Amp × 3 × 3600 s
= 777 600 J = 777.6 kJ.
Sanfoundry Global Education & Learning Series – Thermodynamics.
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