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# NHPC JE’21 ME: Daily Practices Quiz. 27-Sep-2021

## NHPC JE Recruitment 2021

National Hydroelectric Power Corporation (NHPC) has released the recruitment notification for engagement of following posts such as Senior Medical Officer, Assistant Rajbhasha Officer, Junior Engineer & Sr. Accountant posts. NHPC expects application from High Performing, Dynamic & Achievement-Oriented Professionals candidates to fill up these 173 vacancies.

### NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 27-Sep-2021

Quiz: Mechanical Engineering
Exam: NHPC JE
Topic: TOM and HT

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

Q1. In which of the following process plasticity must be considered in designing for processes except
(a) Autofrettage
(b) Shrink fitting
(c) Rotating shaft
(d) Over-speeding of rotor disk

Q2. The transmission angle is minimum and maximum respectively, when the crank angle with the fixed link is
(a) 0° and 270°
(b) 90° and 270°
(c) 0° and 180°
(d) 0° and 90°

Q3. The length of the links of a 4-bar linkage with revolute pairs only are p, q, r and s units. Given that p<q<r<s. Which of these links should be the fixed one, for obtaining a ‘double crank’ mechanism?

Q4. According to Kennedy’s theorem, the instantaneous centres of three bodies having relative motion lie on a
(a) curved path
(b) straight line
(c) point
(d) approximate straight line

Q5. A satellite float in deep space with very high velocity. It will continuously lose heat by
(a) convection
(b) conduction and convection

Q6. Consider the following statements:
1. The thermal conductivity of a material is its ability to conduct heat
2. The thermal conductivity can be defined as the rate of heat transfer through a unit thickness of the material per unit area.
3. In solids, heat conduction is due to lattice vibrational energy as well as energy transported via free flow of electrons.
4. Convection involves combined effect of conduction and fluid motion.
Which of the above statements are valid?
(a) 1 and 2
(b) 2, 3 and 4
(c) 1, 3 and 4
(d) 3 and 4

### Solutions

S1. Ans (c)
Sol. Chances of plastic deformation is negligible for a rotating shaft if the system is balanced.

S2. Ans (c)
Sol.

S3. Ans (a)
Sol.

For Class- I
If shortest link (s) is fixed then we obtain double crank Mechanism.
If link opposite to shortest link (s) is fixed then we obtain double rocker Mechanism
If link other than shortest or opposite to shortest link is fixed then we obtain crank- rocker Mechanism.
For class-II
By fixing any link, we obtain double rocker Mechanism.

S4. Ans (b)
Sol.
Kennedy’s theorem states that when three links are in relative motion then the I – center of three links will lie on the same line.

S5. Ans (c)
Sol. As there is no medium in space for conduction and convection heat transfer to take place, hence heat can be continuously lost by radiation heat transfer.

S6. Ans (c)
Sol. Thermal conductivity of a material is its ability to conduct heat and can be defined as the rate of heat transfer for unit change of temperature from unit thickness per unit area. Conduction in solid is a combination of lattice vibration and electron motion. Convection heat transfer takes place through combined effect of conduction and motion of fluid.

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