Heat and Thermodynamics (Physics) Part-I

Total Questions: 50

21. In cold countries, alcohol is preferred to mercury as a thermometric liquid because : [U.P.P.C.S. (Pre) 1997]

Correct Answer: (a) Alcohol has a lower freezing point
Solution:

There are lots of reasons for using alcohol than mercury as thermometric liquids. Some alcohol has a very low freezing point of about -112°C and therefore is suitable to record very low temperature.

Thus, in cold countries, alcohol is preferred to mercury as a thermometric liquid.

22. Which one of the following is used as an antifreeze for the automobile engines? [U.P.P.C.S. (Spl.) (Pre) 2008, U.P.U.D.A./L.D.A. (Mains) 2010]

Correct Answer: (b) Ethylene glycol
Solution:

Ethylene glycol is an organic molecule most widely used as antifreeze in automobile engines and as an industrial solvent. When it is mixed with water, the freezing point of the mixture is depressed, specifically a mixture of 60% ethylene glycol and 40% water freezes at -45°C. That is why water is not frozen in the engine of cold countries.

23. What is absolute zero temperature? [Jharkhand P.C.S. (Pre) 2010]

Correct Answer: (b) Theoretically the lowest possible temperature.
Solution:

Absolute zero is the lowest possible temperature at which point the atoms of a substance transmit no thermal energy. They are completely at rest. It is 0 on the Kelvin scale, which translates to -273.15 degree Celsius.

24. Expansion during heating- [U.P.P.C.S. (Pre) 2006]

Correct Answer: (c) Decreases the density of the material
Solution:

Density is defined as the ratio between mass and volume or mass per unit volume (Density mass / volume). As the temperature increases, most materials expand or increase their volume. This results in a decrease in density.

25. When ice melts, then- [U.P.P.C.S. (Pre) 2012]

Correct Answer: (b) Volume decreases
Solution:

Elements such as cast iron, ice, antimony, bismuth, and brass when melts, their volume decreases. These type of solids floats in their own melted fluid.

26. The variations in temperature from 0°C to 100°C with respect to time of two liquids P, Q are shown in the graph given below: [I.A.S. (Pre) 1995]

Which of the following statement is correct?

Correct Answer: (d) Q attained the temperature of 100°C faster than P.
Solution:

In above diagram, P denotes a straight line, while point Q denotes a curved line. It is clear that Q attained the temperature of 100°C quicker than P.

27. What is the use of thermostat? [M.P.P.C.S. (Pre) 2005]

Correct Answer: (c) To maintain the temperature
Solution:

Thermostat is a device that automatically regulates temperature. It helps to save energy/power.

28. Thermostat is related to : [U.P.P.C.S. (Pre) 1993]

Correct Answer: (b) Temperature
Solution:

Thermostat is a device that automatically regulates temperature. It helps to save energy/power.

29. Thermostat is a device which : [U.P.P.C.S. (Pre) 2007]

Correct Answer: (c) Automatically regulates the temperature of a system
Solution:

Thermostat is a device which automatically regulates temperature or provides a signal used by another device to regulate temperature.

30. Thermostat ....... is a mean of keeping stable ? [Chhattisgarh P.C.S. (Pre) 2003]

Correct Answer: (b) Temperature
Solution:

Thermostat is a device which automatically regulates temperature or provides a signal used by another device to regulate temperature.