NHPC JE'21 ME: Daily Practices Quiz. 16-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC JE
Topic: Miscellaneous

Each question carries 1 mark
Negative marking: 1/4 mark
Time: 6 Minutes

Q1. An oil of specific gravity 0.9 has viscosity of 0.28 stokes at 38°C. What will be its viscosity in Ns/m²?
(a) 0.2520
(b) 0.0311
(c) 0.0252
(d) 0.0206

Q2. What is the pressure difference between inside and outside a droplet of water?
(a) 2σ/d
(b) 4σ/d
(c) 8σ/d
(d) 12σ/d
Where σ is surface tension and d is the diameter of the droplet.

Q3. A cup of 10 cm height and 5 cm diameter is to be made from a sheet metal of 2 mm thickness. The number of deductions necessary will be
(a) one
(b) two
(c) three
(d) four

Q4. The bending force required for U-bending, V – bending and Edge – bending will be in the ratio of
(a) 1: 2: 0.5
(b) 2: 1: 0.5
(c) 1: 2: 1
(d) 1: 1: 1

Q5. Which of the following devices complies with the Clausius statement of the second law of thermodynamics?
(a) Closed-cycle gas turbine
(b) Internal combustion engine
(c) Steam power plant
(d) Domestic refrigerator

Q6. Superheating of the steam is done at
(a) Constant temperature
(b) Constant volume
(c) Constant pressure
(d) Constant entropy

Solutions

S1. Ans (c)
Sol. Dynamic viscosity,
μ=ρυ=(0.9×1000)×(0.28×10^(-4) )
=0.0252 Ns/m²

S2. Ans (b)
Sol. Pressure difference between inside and outside a droplet of water = 4σ/d
∵ Bursting force = p×πd²/4
Resisting force = σ ×π d
Bursting force= Resisting force
p×πd²/4=σ×πd
or p=4σ/d

S3. Ans.(c)
Sol. D=√(d^2+4dh)=√(5^2+4×5×10)=15
Limiting draw ratio=D/d=15/5=3
The number of deductions necessary will be three.

S4. Ans. (b)
Sol. The bending force required for U-bending, V – bending and Edge – bending will be in the order of
U – bending > V – bending > Edge – bending

S5. Ans. (d)
Sol. Clausius statement: It is impossible to construct a cyclic device which works on a cycle and produce no other effect other than heat transfer from a cold body to a hot body.
Heat Pump and Refrigerator work on Clausius statement of second law of thermodynamics.

S6. Ans. (c)
Sol. Superheating of the steam is done at constant pressure.