NHPC JE’21 ME: Daily Practices Quiz. 12-Oct-2021

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NHPC-JE’21 ME: Daily Practices Quiz

NHPC-JE’21 ME: Daily Practices Quiz 12-Oct-2021

Quiz: Mechanical Engineering
Exam: NHPC
Topic: Miscellaneous

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

Q1. The minimum number of teeth on pinion in case of 20° full depth involute gear is used is
(a) 18
(b) 14
(c) 32
(d) 12

Q2. A thin plate has been placed parallel to flow direction. The relative magnitude of friction and pressure drags will be
(a) Negligible friction as well as pressure drag
(b) Negligible pressure drag and maximum friction drag
(c) Maximum pressure drag and negligible friction drag
(d) Pressure drag equals the friction drag

Q3. A turbine pump is basically a centrifugal pump equipped additionally with
(a) backward curved blades
(b) vaned diffusion casing
(c) inlet guide blades
(d) adjustable blades

Q4. Which one of the following relationships defines the Helmholtz function F?
(a) F=H+ TS
(b) F=H– TS
(c) F=U – TS
(d) F= U+ TV

Q5. Detonation in the SI engine becomes severe during
(a) Low load and high speed
(b) High load and high speed
(c) Low load and low speed
(d) High load and low speed

Q6. Sialon ceramic is used as:
(a) Cutting tool material
(b) Creep resistant
(c) furnace linens
(d) High strength

Solutions

S1. Ans. (a)
Sol.
System of gear Minimum number of teeth on pinion
20° full depth involute gear 18
20° Stub involute gear 14
〖14 1/2〗^°full depth involute gear 32
〖14 1/2〗^° composite gear 12

S2. Ans (b)
Sol. A thin plate has been placed parallel to flow direction. That body is known as streamlined body, and the relative magnitude of friction drag will be maximum and that of pressure drag will be minimum.

S3. Ans (b)
Sol. A turbine pump in basically a centrifugal pump equipped additionally with vaned diffusion casing.

S4. Ans (c)
Helmholtz function F
F=U – TS, it is applicable for closed system
Gibbs Function
G=H-TS, it is applicable for open system

S5. Ans (d)
Sol. Detonation in SI engine will become severe at high load and low speed because at higher loads, the temperature of cylinder and combustion chamber walls will be higher and hence temperature of the end charge will be more which increases knocking tendency in SI engine. And at lower engine speed, longer will be the absolute time for the flame to traverse the cylinder which increases the time available for pre flame reactions, hence the tendency to knock increases.

S6. Ans.(a)
Sol. Si Al ON: It is silicon nitride-based cutting tool materials with aluminium and oxygen additions. This tool material is tougher than alumina. Aerospace alloys and nickel-based gas turbine discs can be machined using sialon tool bit at a cutting speed of 200 -300 m/mt.

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