MCQS Mechanical Engineering
1. Which dimensionless number has the significant role in forced convection
(a) Match number
(b) Reynold number
(c )Prandtl number
(d)Pecklet number
Ans. C
2. A composite wall consists of three different materials having thermal conductivities K,2 K and 4K repectively. The ratio of temoerature drop across different materials will be
(a) 1 : 1 : 1
(b) 1 : 2 : 4
(c )4 : 2 : 1
(d)2 : 4 : 1
Ans. C
3. According to Fourier's law , the quantity of heat flow through a surface area 'A' and thickness'x' is given by the relation
(a) Q= -KA(dt/dx)
(b)Q == A/k (dt/dx)
(c )Q = -A (dx/dt)
(d) Q = -KA(dx/df)
Ans. A
4. A Fin will be Effective only when Biot Number is
(a) Less Than One
(b) Equal To One
(C )More Than One
(d)Infinite
Ans. A
5. On a heat transfer surface , fins are provided to
(a) increase temperature radient so as to enhance heat transfer
(b) increase turbulence in flow for enhancing heat transfer
(c )increase surface area to promote the rate of heat transfer
(d) decrease the pressure drop of the fluid
Ans. C
6. Which one of the following is electrically most conductive
(a) Copper
(b) Silver
(c )Aluminium
(d) Gold
Ans. B
7. The following has least value of conductivity
(a) Rubber
(b) Air
(c )Water
(d) Plastic
Ans. B
8. with rise in temperture thermal conductivity of solid materials
(a) Decreases
(b) Increases
(c )Remains constant
(d) Cannot be predicted
Ans. A
9. The rate of heat transfer from a soild surface to a flud is obtained from
(a) Newton's law of cooling
(b) Fouries's law
(c ) Kirchhoff's law
(d) Stefan's law
Ans. A
10. Heat convection in gase is due to
(a) The elastic impacts of molecules
(b) The motion of electrons
(c )The mixing motion of different parts of a fluid
(d) The electromagnetic waves
Ans. C
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