# Laws of Heat Transfer - Radiation - MCQs with Answers

## Laws of Heat Transfer – Radiation - MCQs with Answers

Q1. How does the radiation heat transfer occur through perfect vacuum?

a. by light waves
b. by electromagnetic waves
c. both a. and b.
d. none of the above

ANSWER: c. both a. and b.

Q2. The Stefan-Boltzmann law of thermal radiation is applicable for

a. white body
b. gray body
c. black body
d. all the bodies

ANSWER: c. black body

Q3. According to the Stefan-Boltzmann law of thermal radiation for a perfect radiator, the rate of radiant energy per unit area is proportional to

a. the temperature of that radiator
b. the square of the temperature of that radiator
c. the cube of the temperature of that radiator
d. the fourth power of the temperature of that radiator

ANSWER: d. the fourth power of the temperature of that radiator

Q4. In the equation for the rate radiant heat energy from a perfect radiator

q = σ A T4

the constant σ is called as

a. Black body constant
c. Stefan-Boltzmann constant
d. none of the above

ANSWER: c. Stefan-Boltzmann constant

Q5. What should be the temperature of black body to emit radiant energy which is independent of the conditions in the surroundings?

a. temperature of black body should be less than zero
b. temperature of black body should be more than zero
c. temperature of black body should be equal to zero
d. all of the above

ANSWER: b. temperature of black body should be more than zero

Q6. Consider two black bodies at temperatures T1 and T2 (T1 > T2) having same surface area A, are placed in vacuum. What will be the correct formula for net rate of radiant heat transfer between these surfaces?
Where σ is a Stefan-Boltzmann constant

a. q = σ A (T1 – T2)4
b. q = σ A (T14 – T24)
c. q = σ A (T1 – T2)
d. none of the above

ANSWER: b. q = σ A (T14 – T24)

Q7. Gray body can emits radiation

a. at higher rate than the black body
b. at lower rate than the black body
c. at equal rate than the black body
d. cannot predict