Search
.Management Sciences
Category: Heat Transfer
The total emissivity power is .defined as the total amount of radiation emitted by a black body per unit_______________?
A. temperature
B. thickness
C. area
D. time
E. area and time
Thermal conductivity of a material may be defined as the________________?
A. quantity of heat flowing in one second through one cm cube of material when opposite faces ^re maintained at a temperature difference of 1°C
B. quantity of heat flowing in one second through a slab of the material of area one cm square, thickness 1 cm when its faces differ in temperature by 1°C
C. heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
D. all of the above
E. none of the above
Depending on the radiating properties, a body will be opaque when _________________?
A. p = 0, x = 0 and a = 1
B. p=l,x = 0anda = 0
C. p = 0, x = 1 and a = 0
D. x – 0, a + p = 1
E. a=0,x + p= 1.
where a = absorptivity, p = reflectivity, X = transmissivity
A perfect black body is one which_______________?
A. is black in colour
B. reflects all heat
C. transmits all heat radiations
D. abslprbs heat radiations of all wave lengths falling on it
E. fully opaque
Unit of thermal conductivity in M.K.S. units is ___________________?
A. kcal/kg m2 °C
B. kcal-m/hr m2 °C
C. kcal/hr m2 °C
D. kcal-m/hr °C
E. kcal-m/m2 °C
Heat transfer by radiation mainly depends upon___________________?
A. its temperature
B. nature of the body
C. kind and extent of its surface
D. all of the above
E. none of the above
Heat transfer in liquid and gases takes place by_____________________?
A. conduction
B. convection
C. radiation
D. conduction and convection
E. convection and radiation
Thermal conductivity of water at 20°C is of the order of_____________________?
A. 0.1
B. 0.23
C. 0.42
D. 0.51
E. 0.64
Stefan Boltzmann law is applicable for heat transfer by __________________?
A. conduction
B. convection
C. radiation
D. conduction and radiation combined
E. convection and radiation combined
Cork is a good insulator because it has___________________?
A. free electrons
B. atoms colliding frequency
C. low density
D. porous body
E. all of the above
Recent Comments