Heat Test

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Heat Test - 9

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Weekly Quiz Competition

Question 1
1 / -0

Oxygen boils at – 183°C. This temperature is approximately

A
215°F

B
– 297°F

C
329°F

D
361°F

Solution

Oxygen boils at –183°C.
C = (F – 32)
Or F =
F =
= – 297.4°F or – 297°F
Question 2
1 / -0

The freezing point on a thermometer is marked as 20° and the boiling point as 150°. A temperature of 60°C on this thermometer will be read as

A
40°

B
65°

C
98°

D
110°

Solution

Suppose:
P = Ax + B
When x = 0 and P = 20^oC, then
B = 20^oC
When x = 100^oC and P = 150^oC, then
150 = 100A + 20
A = 1.3
Now, when x = 60^oC,
P = 1.3 x 60 + 20 = 98^oC
Question 3
1 / -0

The study of physical phenomena at low temperature (below liquid nitrogen) is called

A
refrigeration

B
radiation

C
cryogenics

D
pyrometry

Solution

Cryogenics is the study of physical phenomena at low temperatures.
Question 4
1 / -0

Gaps are kept between railway tracks because

A
in winters, the tracks may contract

B
friction is produced and the speed of train may not increase beyond a limit for safety reasons

C
the replacement of the track is easier when there is gap in the track

D
expansion of tracks takes place and some free space is required for free expansion

Solution

Gaps are kept between railway tracks because of thermal heating. The tracks expand and require some space to expand.
Question 5
1 / -0

During severe winter in low temperature zones of the world, the superficial parts of the lakes are frozen leaving water below. The freezing at the bottom is prevented because

A
conductivity of ice is low

B
water has large latent heat of fusion

C
water has large specific heat

D
temperature of the earth at the bottom of lake is high

Solution

The freezing at the bottom is prevented because water, when it freezes becomes less dense and hence rises to the top. This sheet of ice on the top acts as a barrier to the water at the bottom.
Question 6
1 / -0

When water is heated from 0°C, its volume

A
increases

B
decreases till 4^oC

C
remains unchanged

D
first increases, then decreases

Solution
Question 7
1 / -0

If we touch a piece of copper and another piece of glass at 40^oC, then copper will feel hotter because

A
copper has higher atomic mass

B
density of copper is more

C
our body temperature is nearly 37^oC

D
copper has higher specific heat

Solution

Copper has a higher specific heat than glass. It means that the heat required to raise the temperature of copper by one degree centigrade is more for copper as compared to glass. Hence, it feels hotter.
Question 8
1 / -0

The radiating power of a body depends on

A
nature of the surface

B
difference in temperature of body

C
area of the surface

D
all of the above

Solution

Radiating power of a body depends upon the following factors:
(a) nature of the surface
(b) difference in temperature of the body and the surroundings
(c) area of the surface
Hence, all of the above is the correct option.
Question 9
1 / -0

If the temperature of the sun is doubled, the rate of energy received on earth will be increased by a factor of

A
2

B
4

C
8

D
16

Solution

The radiation emitted is directly proportional to the 4^th power of temperature of the body.
If sun`s temperature is doubled, then its radiation will become 16 times.
Question 10
1 / -0

A ball A has twice the diameter as another ball B of the same material and with same surface finish. If both A and B balls are heated to the same temperature, and allowed to cool by emitting radiations, then

A
rate of cooling of A is same as that of B

B
rate of cooling of A is twice that of B

C
rate of cooling of A is half that of B

D
rate of cooling of A is four times that of B

Solution

Rate of cooling of A is twice that of B because rate of emitting radiations is directly proportional to S, area of the body.
Question 11
1 / -0

Water is used in hot water bottles because

A
its specific heat is high

B
it is easy to heat

C
it is easily available

D
it is not harmful to health

Solution

Water is used in hot water bottles because its specific heat is very high.
Question 12
1 / -0

The water equivalent of a body is 10 g. Its thermal capacity is

A
10 J/K

B
10 Cal/K

C
10 K Cal/K

D
10 g/K

Solution

The water equivalent of a body is 10 g. Its thermal capacity is 10 Cal/K
Question 13
1 / -0

A liquid of mass m and specific heat c is heated to a temperature T. Another liquid of mass (m/2) and specific heat 2c is heated to a temperature 2T. If these two liquids are mixed, the resulting temperature of the mixture will be

A
(2/3)T

B
(8/5)T

C
(3/5)T

D
(3/2)T

Solution

Let the temperature of mixture be t.

The heat equation for mixing two liquids to make the mixture:
Question 14
1 / -0

During severe winter, water in a lake starts freezing ___

A
first at the bottom

B
first at the surface

C
as a whole

D
first in the middle

Solution

Water in the lake starts freezing at the surface because ice is less dense than water and hence rises to the surface.
Question 15
1 / -0

During melting process, heat given to a body is utilized in

A
increasing temperature

B
increasing density

C
increasing the average distance between molecules

D
decreasing the mass of the body

Solution

During melting process the heat supplied to a body is utilized in changing the phase of a body. As in melting, the body is changing from solid to liquid, and solid is more dense and liquid is less dense, therefore, the average distance between the molecules increases.
Question 16
1 / -0

One gram of ice at 0°C is converted into steam at 100°C. The amount of heat required to do so is(Latent heat of fusion of ice = 80 cal/ g)

A
80 cal

B
536 cal

C
616 cal

D
0.6439 kcal

Solution

Latent heat of fusion of ice = 80 cal/ g
Hence, from ice at 0°C to water at 0°C
Heat required = 80 cal
Heat required to increase the temperature of water from 0°C to 100°C
= 1 0.239 100
= 23.9 cal
Water now converts to steam at 100°C,
= 1 540
= 540 cal
Total = 80 + 23.9 + 540
= 643.9 cal
= 0.6439 kcal
Question 17
1 / -0

A horizontal cylinder has two sections of unequal cross-sections, in which two pistons can move freely. The pistons are joined by a string. A gas is trapped between the pistons. If this gas is heated, the pistons will

A
move to the left

B
move to the right

C
remain stationary

D
either (1) or depending on the initial pressure of the gas

Solution

Piston will move to the right because area of the right side section is more and P =
Therefore, F = P A
Therefore, force on the right side will be more for the same pressure.
Question 18
1 / -0

Which device can convert electrical energy into heat?

A
Radiator

B
Converter

C
Generator

D
Resistor

Solution

Resistor converts electrical energy into heat.
Question 19
1 / -0

The boiling point of water can be raised by

A
increasing heat supply

B
increasing quantity of water

C
increasing pressure

D
reduced pressure

Solution

Boiling point of water can be raised by increasing pressure because pressure is directly proportional to temperature.
Question 20
1 / -0

Sprinkling of water reduces the temperature of a closed room because

A
temperature of water is less than that of the room

B
specific heat of water is high

C
water has high latent heat of vapourisation

D
water is a bad conductor of heat

Solution

Temperature decreases because sprinkled water absorbs heat from the air and vapourises and also, for water, the latent heat is very high.