Heat and Mass Transfer
Depending on the radiating properties, a body will be black when (Where a = absorptivity, p = reflectivity, X = transmissivity.)

P= 1, T = 0 and a = 0
P = 0, x = 1 and a = 0
X = 0, a + p = 0
P = 0, x = 0 and a = 1

ANSWER DOWNLOAD EXAMIANS APP

Heat and Mass Transfer
The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)

Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]
Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)
Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)
Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)

ANSWER DOWNLOAD EXAMIANS APP

Heat and Mass Transfer
Thermal conductivity of a material may be defined as the

All of these
Heat conducted in unit time across unit area through unit thickness when a temperature difference of unity is maintained between opposite faces
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
Quantity of heat flowing in one second through one cm cube of material when opposite faces are maintained at a temperature difference of 1°C

ANSWER DOWNLOAD EXAMIANS APP

Heat and Mass Transfer
Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

k.
k.
k. (dx/dT)
k. (dT/dx)
(dT/dx)
(dx/dT)

ANSWER DOWNLOAD EXAMIANS APP
MORE MCQ ON Heat and Mass Transfer