# Engineering Physics Questions and Answers – Thermal Expansion

This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Thermal Expansion”.

1. A faulty thermometer has its fixed points marked as 5° and 95°. The temperature of a body as measured by the faulty thermometer is 59°. Find the correct temperature of the body on a Celsius scale.
a) 60°C
b) 40°C
c) 20°C
d) 0°C

Explanation: (TC-0)/(100-0)=(Temperature on faulty scale-Lower fixed point)/(Upper fixed point-Lower fixed point)
(TC-0)/100=(59-5)/(95-5)=54/90
TC=60°C.

2. Temperature is a microscopic concept.
a) True
b) False

Explanation: Temperature is a macroscopic concept. It is related to the average kinetic energy of a large number of molecules forming a system. It is not possible to define the temperature for a single molecule.

3. The thermometer bulb should have ___________
a) High heat capacity
b) No heat capacity
c) Small heat capacity
d) Varying heat capacity

Explanation: The thermometer bulb having small heat capacity will absorb less heat from the body whose temperature is to be measured. Hence the temperature of that body will practically remain unchanged.

4. Calorie is defined as the amount of heat required to raise the temperature of 1g of water by 1°C and it is defined under which of the following conditions?
a) From 14.5°C to 15.5°C at 760mm of Hg
b) From 98.5°C to 99.5°C at 760mm of Hg
c) From 13.5°C to 14.5°C at 76mm of Hg
d) From 3.5°C to 4.5°C at 76mm of Hg

Explanation: One calorie is defined as the heat required to raise the temperature of 1g of water from 14.5°C to 15.5° at 760mm of Hg.

5. Compared to burn due to air at 100°C, a burn due to steam at 100°C is ___________
a) More dangerous
b) Less dangerous
c) Equally dangerous
d) Not dangerous

Explanation: Compared to burn due to air at 100°C, a burn due to steam at 100°C is more dangerous due to the additional heat possessed by steam.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

6. 540g of ice at 0°C is mixed with 540g of water at 80°C. What is the final temperature of the mixture?
a) 0°C
b) 40°C
c) 80°C
d) Less than 0°C

Explanation: Heat gained by ice = Heat lost by water at 80°C
540×80+540×1×θ=540×1×(80-θ)
θ=0°C.

7. An ideal black body is thrown into a furnace. The black body is room temperature. It is observed that ___________
a) Initially, it is darkest body and at later times the brightest
b) At all times it is the darkest body
c) It cannot be distinguished at all times
d) Initially, it is the darkest body and at later it cannot be distinguished

Explanation: Initially at lower temperature, it absorbs the entire radiations incident upon it. So, it is the darkest body. At later times, when it attains the temperature of the furnace, the black body radiates maximum energy. It appears brightest of all bodies.

8. If the sun were to increase in temperature from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously, will be ___________
a) 4
b) 16
c) 32
d) 64

Explanation: Energy radiated by the sun per second,
E = σAT4= σ×4πR2×T4
When its radius and temperature change to 2R and 2T respectively,
E=σ×4π(2R)2×(2T)4
E/E=64.

9. On a hilly region, water boils at 95°C. What is the temperature expressed in Fahrenheit?
a) 100°F
b) 203°F
c) 150°F
d) 20.3°F

Explanation: (F-32)/9=C/5=95/5
F = 171+32 = 203°F.

10. A composite rod made of copper (1.8×10(-5) K(-1)) and steel (α=1.2×10(-5) K(-1)) is heated. Then ___________
a) It bends with steel on concave side
b) It bends with copper on concave side
c) It does not expand
d) Data is insufficient

Explanation: αcoppersteel
Copper expands more than steel. So rod bends with copper on convex side and steel on concave side.

11. Temperatures of two stars are in ratio 3:2. If wavelength of maximum intensity of first body is 4000 Å, what is corresponding wavelength of second body?
a) 9000 Å
b) 6000 Å
c) 2000 Å
d) 8000 Å

Explanation: ((ʎm))/ʎm = T/T = 3/2
m)=3/2 ʎm
m)=3/2×4000=6000Å.

12. A piece of blue glass heated to a high temperature and a piece of red glass at room temperature, are taken inside a room that is dimly lit, then ___________
a) The blue piece will look blue and red will look as usual
b) Red looks brighter and blue looks ordinary blue
c) Blue shines like brighter red compared to the red pieces
d) Both the pieces will look equally red

Explanation: According to Stefan’s law, E is proportional to T4
As the temperature of blue glass is more than that of red glass, so it will appear brighter than red glass.

Sanfoundry Global Education & Learning Series – Engineering Physics.

To practice all areas of Engineering Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]