Heat Transfer Concepts Quiz

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Questions and Answers

What is the correct uniform temperature of rod F when rods E and G are maintained at temperatures θ1 and θ2 respectively?

(2θ1 + θ2)/3

(3θ1 + θ2)/4 (correct)

(θ1 + 3θ2)/4

θ1

Which of the following statements correctly describes the specific heat capacity of aluminium compared to copper?

Copper has a higher specific heat capacity than aluminium.

Aluminium has a higher specific heat capacity than copper. (correct)

Both have the same specific heat capacity.

Aluminium has half the specific heat capacity of copper.

What is the rate of cooling of the metal block immediately after the heater is switched off?

1.0 °C/s

0.5 °C/s

0.1 °C/s

0.2 °C/s (correct)

What is the relationship between the density of copper and aluminium given that the density of copper is 3.4 times that of aluminium?

Copper is denser than aluminium. Signup and view all the answers

How much maximum heat can a hot body lose if the specific heat capacity is 's' and the mass is 'm'?

ms(T1 - T0) Signup and view all the answers

Which of the following assumptions applies to the cooling process of the hollow copper sphere?

Surrounding temperature is constant. Signup and view all the answers

What is the significance of the parameter 'k' in the cooling process of the hot body?

It determines the time constant for cooling. Signup and view all the answers

How does the rate of heat loss from the aluminium sphere compare to that from the copper sphere, if they have the same surface area and emissivity?

The aluminium loses heat faster. Signup and view all the answers

What is the formula to calculate thermal conductance for radial flow of an annular cylinder?

$\frac{K \cdot \pi (r_2^2 - r_1^2)}{\lambda}$ Signup and view all the answers

If a heater is switched off, which condition describes the power radiated by the block just after the heater is switched off?

It is equal to the power supplied by the heater. Signup and view all the answers

Which variable affects the amount of energy radiated by a human body?

Body temperature Signup and view all the answers

What is the relationship between the inner temperature T1 and the outer temperature T2 in the hollow tube scenario?

T2 is greater than T1. Signup and view all the answers

What is required to calculate the time for ice to melt completely in the metallic cylindrical vessel?

The thermal conductivity of the cylinder and its length Signup and view all the answers

Given the emissivity of a radiator and its surface area, what parameter is necessary to calculate the energy radiated?

The surface temperature of the radiator Signup and view all the answers

What does the latent heat of fusion signify in the context of the cylindrical vessel with ice?

The heat required to change ice at 0°C to water at 0°C Signup and view all the answers

For a uniform cylinder on a metal plate, which factor primarily determines the time for temperature increase in the plate?

The specific heat capacity of the plate Signup and view all the answers

At what rate is radiation emitted by the radiator when its temperature is 50°C?

1040 W/m² Signup and view all the answers

What is the rate of radiation absorbed by the radiator in a room where the walls are at 22°C?

290 W/m² Signup and view all the answers

What is the net rate of radiation from the radiator?

750 W/m² Signup and view all the answers

At what net rate does a man's body lose heat if his skin temperature is 28°C in a 20°C room?

60 W Signup and view all the answers

What is the power required by the electric heater in a room with total wall area 137 m² to maintain a temperature of 20°C?

800 W Signup and view all the answers

In a rod with heat conductivity coefficient varying as K = α/T, what is the general form of the temperature function T(x)?

T(x) = T1 + (T2 - T1)(x/λ) Signup and view all the answers

What is the expected temperature difference behavior between the two chunks of metal in thermal equilibrium?

Asymptotic approach to zero Signup and view all the answers

What is the combined thermal conductivity factor for the three layers of wall materials keeping heat from escaping the electric heater?

0.47 W/m°C Signup and view all the answers

What is the correct expression for the change in temperature over time as given?

ΔT = ΔT₀ e^(-αt) Signup and view all the answers

Given a ratio of 1:4, which option corresponds to this ratio if it involves temperature?

For every 1°C, there are 4 units of heat loss Signup and view all the answers

Which of the following expressions correctly represents the thermal balance equation?

q = (α/λ) ln(r₂/r₁) Signup and view all the answers

What is the value of mechanical power when it is stated as 539 W, 375 W, and 164 W?

It indicates total power for different applications Signup and view all the answers

In the expression mCL, what do the variables represent?

m is mass, C is heat capacity, L is latent heat Signup and view all the answers

Study Notes

Heat Transfer

Heat Transfer is the movement of thermal energy between objects at different temperatures.
Thermal Conductivity (K) is the ability of a material to conduct heat.
Heat Flow Rate is the amount of heat transferred per unit time.
Newton's Law of Cooling states that the rate of heat loss from an object is proportional to the temperature difference between the object and its surroundings.
Stefan-Boltzmann Law describes the power radiated by a black body, which is proportional to the fourth power of its absolute temperature.
Emissivity is a measure of how well a material radiates energy like a black body.
Thermal Conductance is the rate of heat flow through a material per unit temperature difference.
Heat Capacity is the amount of heat required to raise the temperature of a substance by one degree Celsius.
Specific Heat Capacity is the amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.
Latent Heat of Fusion is the amount of heat required to melt a solid at its melting point.
Thermal Resistance is the inverse of thermal conductance.
Heat Flux is the rate of heat flow per unit area.

Questions

Question 1 involves a system of rods with different thermal conductivities. The aim is to find the temperature of rod F and the rate of heat flow through the system.
Question 2 involves finding the rate of heat flow through a rod with a constant thermal conductivity.
Question 3 deals with two spheres of different materials (aluminium and copper) and compares their rates of heat loss and temperature decrease.
Question 4 involves a hot body cooling down in a surrounding temperature and is a classic application of Newton's Law of Cooling, requiring the calculation of total heat loss and time to lose 50% of the maximum heat.
Question 5 asks for the time taken for a hollow copper sphere to cool down under given conditions, using Stefan-Boltzmann Law for radiative heat transfer.
Question 6 analyzes a metal block being heated and then cooled, requiring the determination of heater power, radiated power, and time of heating.
Question 7 examines a hollow tube with varying radii and asks for the heat flow rate through the tube walls.
Question 8 involves calculating the thermal conductance of an annular cylinder.
Question 9 calculates the thermal conductance for a spherical shell.
Question 10 concerns a cylindrical vessel filled with ice and immersed in air, asking for the time taken for the ice to melt.
Question 11 involves a cylinder placed on a metal plate and determining the time taken for the plate's temperature to rise.
Question 12 calculates the energy radiated per second by a human body, assuming it as an ideal radiator.
Question 13 analyzes a household radiator, calculating its emitted radiation, absorbed radiation, and net rate of radiation.
Question 14 addresses a man sitting in a room and determines the rate at which his body loses heat.
Question 15 deals with an electric heater maintaining a room's temperature and finding its power requirement.
Question 16 involves a rod with variable thermal conductivity, requiring the derivation of temperature distribution and heat flow density.
Question 17 has two chunks of metal connected by a rod, asking for the change in temperature difference over time.

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Description

Test your knowledge on the principles of heat transfer, including concepts like thermal conductivity, heat flow rate, and Newton's law of cooling. This quiz covers key laws and definitions critical for understanding thermal energy movement.