Transmission of Heat

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What is the unit of thermal conductivity in S.I. system?

J/m-sec-K

Cal/m-sec-oC

W/m-K (correct)

kcal/m-sec-K

What is the dimension of thermal conductivity?

[M1L32]

[MLT31] (correct)

[L2]

[L1]

What determines the magnitude of thermal conductivity of a material?

Temperature of the material

Length of the material

Cross-sectional area of the material

Nature of the material (correct)

What is the characteristic of good conductors of heat?

Large thermal conductivity due to large number of free electrons Signup and view all the answers

What is the temperature difference between the opposite faces of a rod when Q = K, given A = 1m2, t = 1 sec, and l = 1m?

1oC Signup and view all the answers

What is the effective thermal conductivity of a system with a cylinder of radius R made of a material of thermal conductivity K1 surrounded by a cylindrical shell of inner radius R and outer radius 2R made of material of thermal conductivity K2?

(K1 + 3K2) / 4 Signup and view all the answers

What is the temperature of the interface of a compound wall in terms of their thermal resistances R1 and R2?

R1θ2 + R2θ1 / (R1 + R2) Signup and view all the answers

What is the equivalent thermal conductivity of a system with two materials in parallel combination?

K1A1 + K2A2 / (A1 + A2) Signup and view all the answers

What is the heat current in a system with a temperature gradient?

KAΔT / L Signup and view all the answers

What is the relationship between the thermal conductivity and thermal resistance of a material?

R = l / (KA) Signup and view all the answers

In series combination of conductors, what is the relation between the heat current in each conductor?

Heat current is the same in all the conductors Signup and view all the answers

What is the equivalent thermal conductivity for n slabs of equal length in series combination?

K = 1 / (1/K1 + 1/K2 + ... + 1/Kn) Signup and view all the answers

In a series combination of conductors, what is the relation between the temperature gradient and the thermal conductivity?

Temperature gradient is inversely proportional to the thermal conductivity Signup and view all the answers

If two slabs of equal length are connected in series, what is the equivalent thermal conductivity?

K = 2 / (1/K1 + 1/K2) Signup and view all the answers

What is the correct expression for the equivalent thermal conductivity for two slabs of equal length in parallel combination?

K = K1 + K2 Signup and view all the answers

In a series combination of slabs, what is the correct expression for the equivalent thermal conductivity?

$\dfrac{K_1K_2}{K_1 + K_2}$ Signup and view all the answers

What is the relation between the heat current and the temperature gradient in a slab?

Heat current is directly proportional to the temperature gradient Signup and view all the answers

In a parallel combination of slabs, what is the correct expression for the equivalent thermal conductivity?

$K_1 + K_2$ Signup and view all the answers

What is the correct expression for the temperature gradient in a slab?

$\dfrac{dT}{dx} = \dfrac{Q}{KA}$ Signup and view all the answers

What is the relation between the equivalent thermal conductivity and the thermal resistances of two slabs in parallel combination?

$K = \dfrac{1}{R_1} + \dfrac{1}{R_2}$ Signup and view all the answers

If three slabs of equal lengths are connected in series, what is the equivalent thermal conductivity in terms of their thermal conductivities K1, K2, and K3?

K = (K1K2K3)/(K1K2 + K2K3 + K1*K3) Signup and view all the answers

In a parallel combination of two slabs of equal area, what is the equivalent thermal conductivity in terms of their thermal conductivities K1 and K2?

K = K1 + K2 Signup and view all the answers

What is the heat current in a system with a temperature gradient Δθ and thermal conductivity K, cross-sectional area A, and length l?

Q = KA(Δθ)/l Signup and view all the answers

What is the temperature gradient in a system with a heat current Q, thermal conductivity K, cross-sectional area A, and length l?

Δθ = Ql/(KA) Signup and view all the answers

If two slabs of equal lengths are connected in series, what is the equivalent thermal conductivity in terms of their thermal conductivities K1 and K2?

K = (K1*K2)/(K1 + K2) Signup and view all the answers

In a series combination of two slabs of equal length, what is the equivalent thermal conductivity if the thermal conductivities of the slab are K1 and K2?

$\frac{K_1K_2}{K_1+K_2}$ Signup and view all the answers

In a parallel combination of two slabs of equal length, what is the equivalent thermal conductivity if the thermal conductivities of the slab are K1 and K2?

$K_1+K_2$ Signup and view all the answers

In a rod, the heat current is given by Q = KA(θ1 - θ2) / l. What is the correct unit of thermal conductivity in S.I. system?

W/m-K Signup and view all the answers

In a system with a temperature gradient, what is the relationship between the heat current (Q) and the temperature difference (θ1 - θ2)?

Q ∝ θ1 - θ2 Signup and view all the answers

For two slabs of equal length in parallel combination, what is the correct expression for the equivalent thermal conductivity?