Question 1 1 / -0
The length of a rod of aluminium is 1.0 m and its area of cross-section is 5 cm2 . Its one end is kept at 250°C and the other end at 50°C. How much heat will flow in the rod in 5 minutes? (K for Al = 2 × 10-1 kJ/m sec °C)
Solution
K = 2 × 10
- 1 kJ/m sec
o C = 200 J(m sec
o C)
A = 5 × 10
- 4 m
2 T
1 - T
2 = 250 - 50 = 200
o C
t = 5 × 60 = 300 sec
d = 1 m
cal
Question 2 1 / -0
A block of ice at -10°C is slowly heated and converted to steam at 100°C. Which of the following curves represents this phenomenon qualitatively?
Solution
The temperature of ice will first increases from -10°C to 0°C.
Heat supplied in this process will be:
Q
1 = m s
i (10)
Here, m = mass of ice
s
i = specific heat of ice
Then, ice starts melting. Temperature during melting will remain constant (0°C).
Heat supplied in the process will be:
Q
2 = mL L = latent heat of melting
Now, the temperature of water will increase from 0°C to 100°C.
Heat supplied will be:
Q
3 = ms
w (100) s
w = specific heat of water
Finally, water at 100°C will be converted into steam at 100°C and during this process, temperature again remains constant.
The temperature versus heat supplied graph will be as follows:
Question 3 1 / -0
An ice box made of styrofoam (thermal conductivity = 0.01 Jm-1 s-1 K-1 ) is used to keep liquids cool. It has a total wall area, including the lid, of 0.8 m2 and wall thickness of 2.0 cm. A bottle of water is placed in the box, filled with ice. If the outside temperature is 30o C, then the rate of flow of heat into the box is (in J-s-1 )
Question 4 1 / -0
Consider a compound slab consisting of two different materials having the same length and thickness but different thermal conductivities K and 2K. The equivalent thermal conductivity of the slab is (assume them to be connected in series)
Question 5 1 / -0
A copper block of mass 4 kg is heated in a furnace to a temperature 425°C and then placed on a large ice block. The mass of ice that will melt in this process will be (Specific heat of copper = 500 J kg-1 °C-1 and heat of fusion of ice = 336 kJ kg-1 )
Question 6 1 / -0
The temperature at which the Celsius and Fahrenheit scales give the same reading is:
Solution
Let the common temperature is x on both scaled.
Put C = F = x
or 9x = 5x – 160
or 4x = -160
x = -40°
Question 7 1 / -0
The temperatures of equal masses of three different liquids A, B and C are 12°C, 19°C and 28°C, respectively. The temperature when A and B are mixed is 16°C and that when B and C are mixed is 23°C. The temperature when A and C are mixed is
Question 8 1 / -0
In which mode of transmission do heat waves travel along a straight line with the speed of light?
Solution
The energy emitted by a body in the form of radiation on account of its temperature is called thermal radiation. These radiations are heat radiations and travel along straight lines with the speed of light.
Question 9 1 / -0
A brass rod of length 500 mm and diameter 3 mm is joined to a steel rod of same length and diameter at 50°C. If the coefficient of linear expansion of brass and steel are 2.5 x 10-5 °C-1 and 1.25 x 10-5 °C-1 , then change in length of the combined rod at 200°C is
Question 10 1 / -0
An electric water kettle rated 2.1 kW is filled with 1.5 kg of water at 20o C. How many seconds does it take to reach the boiling point of water? Assume that there are no heat losses from the kettle. Specific heat capacity of water is 4200 Jkg-1 K-1
Question 11 1 / -0
Ten moles of an ideal gas at constant temperature 500 K is compressed from 50 L to 5 L. Work done in the process is (Given, R = 8.31 J - mol-1 - K-1 ):
Solution
Work done at constant temperature (i.e., isothermal process),
W = 2.3 nRT log
10 = 2.3 × 10 × 8.31 × 500 × log
10 = -9.6 × 10
4 J
Question 12 1 / -0
The temperature of a body on Kelvin scale is found to be xK. When it is measured by Fahreheit thermometer, it is found to be x o F, then the value of x is :
Question 13 1 / -0
A body cools from 100o C to 70o C in 8 second. If the room temperature is 15o C and assuming Newton's law of cooling to hold true then, the time required for the body to cool from 70o C to 40o C is:
Question 14 1 / -0
We find that the temperature of air decreases as one goes up from the Earth's surface because:
Question 15 1 / -0
At constant pressure, which of the following is true?
Question 16 1 / -0
The temperature, at which the rms velocity of hydrogen is four times of its value at NTP is:
Question 17 1 / -0
Newton's law of cooling holds good only if the temperature difference between the body and the surroundings is:
Question 18 1 / -0
With same initial conditions, an ideal gas expands from volume V1 to V2 in three different ways. The work done by the gas is W1 if the process is isothermal, W2 if isobaric and W3 if the process is adiabatic, then
Question 19 1 / -0
The thermal conductivity of a rod is 2. What is its thermal resistivity?
Solution
Thermal resistivity is reciprocal of thermal conductivity.
Question 20 1 / -0
If we consider the radiations emitted by the human body, then which of the following statements is true?
Question 21 1 / -0
In an adiabatic change, the pressure and temperature of a monoatomic gas are related according to the relation
, where C is equal to:
Question 22 1 / -0
A thermos flask made of stainless steel contains several tiny lead shots. If the flask is quickly shaken up and down several times, the temperature of lead shots:
Question 23 1 / -0
When water is heated from 0° to 10°C, its volume
Solution
Water when heated through 4°C shows anomalous behaviour. When it is heated from 0°C to 4°C, then volume of water decreases and after 4°C volume increases.
Question 24 1 / -0
If the sun becomes twice as hot as it is now then
Solution
As Wave length emitted is inversely proportional to the temperature of the source, As the temperature increases the wavelength will decreases so it will radiate predominantly in the ultraviolet.
Question 25 1 / -0
In terms of mechanical unit, Cp - Cv = ......, where Cp and Cv are principal specific heats.
×
Sign in
Profile
Signout
Get latest Exam Updates 
