Heat Test

Result

Heat Test - 8

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Question 1
1 / -0

The scale of temperature on which temperature is only positive is

A
Fahrenheit

B
Celsius

C
Kelvin

D
Reaumur

Solution

Kelvin scale has all positive readings.
Question 2
1 / -0

Mercury thermometers can be used to measure temperature up to

A
100° C

B
212°C

C
360°C

D
500°C

Solution

Mercury thermometers can be used to measure temperatures up to 360°C, exactly up to 357°C.
Question 3
1 / -0

Pyrometer is an instrument used to measure

A
high temperatures

B
low temperatures

C
specific heat

D
latent heat

Solution

Pyrometer is used to measure high temperatures.
Question 4
1 / -0

A metal plate has a circular hole cut in it. If the plate is heated to a higher temperature, the diameter of the hole will

A
remain unchanged

B
increase

C
decrease

D
increase or decrease depending upon its size

Solution

When a metal plate is heated, it will expand and hence, the circular hole inside it will also expand.
Question 5
1 / -0

Expansion during heating

A
occurs only in solids

B
increases the weight of a material

C
decreases the density of a material

D
occurs at the same rate for all

Solution

Expansion increases the volume for the same mass. Hence, mass per unit volume decreases and therefore, density decreases.
Question 6
1 / -0

A beaker is filled upto brim with water at 4°C. The temperature is increased by a few °C above 4°C and further, it is decreased by few °C below 4°C. What will we observe?

A
The level remains constant in each case.

B
In case I, water overflows while in II case, its level comes down.

C
In case II water overflows while in case in I, its level comes down.

D
Water overflows in both the cases.

Solution

Water has the maximum density at 4°C. Hence, if it is cooled or heated beyond that, its volume increases. Therefore, it expands and overflows.
Question 7
1 / -0

The high thermal conductivity of metal is due to free electrons. The related electron property is

A
it being charged

B
its high average energy

C
its high average thermal speed

D
its low volume

Solution

The high average thermal speed of electrons is responsible for the high thermal conductivity of metals
Question 8
1 / -0

Ventilators are provided at the top of rooms

A
to bring oxygen for breathing

B
so that sunlight may enter the room

C
to maintain convection currents to keep the air fresh in the room

D
to provide an outlet for carbon dioxide

Solution

Ventilators are provided at the top to maintain convection currents to keep the air fresh in the room. This is because convection currents help in the circulation of air as the hot air rises and cold air takes its place at the bottom. Therefore, proper circulation takes place.
Question 9
1 / -0

The temperature of a body is increased from 27°C to 127°C. The radiation emitted by it increases by a factor of

A
(256/81)

B
(15/9)

C
(4/3)

D
(12/27)

Solution

The radiation is directly proportional to T⁴, where T is the temperature in Kelvin.
T₂ = (127 + 273) = 400 K , T₁ = (27 + 273) = 300 K
Hence, it increases by a factor of
=
=
Question 10
1 / -0

In a room, where the temperature is 30°C, a body cools from 61°C to 59°C in 4 minutes. The time taken by the body to cool from 51°C to 49°C will be

A
4 minutes

B
6 minutes

C
5 minutes

D
8 minutes

Solution
Question 11
1 / -0

1 kg of hot water at 76^oC is poured into a calorimeter containing 0.50 kg of water at 14^oC. If the temperature of the mixture is 54^oC, what is the thermal capacity of the calorimeter?

A
180 Joule/⁰C

B
200 Joule/⁰C

C
209 Joule/⁰C

D
280 Joule/⁰C

Solution

Heat released by hot water = Heat absorbed by calorimeter and water in calorimeterHere, s is the specific heat of water and s = 1 calorie/ gram-⁰c = 4.186 Joule/gram-⁰C.

C is the thermal capacity of the calorimeter.

Hence,
Question 12
1 / -0

If 420 J of energy is supplied to 10 g of water, it will raise its temperature by nearly

A
1°C

B
4.7°C

C
10°C

D
42°C

Solution

Heat supplied is:
Heat = 420 J = mC_pΔT
C_p = 4.2 J/g°C
m= 10g
420 = (4.2)(10)ΔT
△T = 10°C
Hence, the correct option is (3).
Question 13
1 / -0

The ratio of densities of two bodies is 5 : 6 and their specific heats are in the ratio 3 : 5. The ratio of their thermal capacities per unit volume is

A
25 : 18

B
1 : 2

C
2 : 1

D
1 : 1

Solution

Q = mc△T

Specific heat of the object is given by

H = mc

Or, we have

H₁: H₂ : : 1 : 2
Question 14
1 / -0

Latent heat of fusion of any body

A
is dependent on pressure

B
is dependent on volume

C
is always the same

D
varies under different conditions

Solution

Latent heat of fusion of any body is always the same.
Question 15
1 / -0

One gram of ice at 0⁰ C is mixed with 1 g of steam at 100⁰ C. Latent heat of fusion of water is 80 cal/g and latent heat of vaporisation is 536 cal/g. After thermal equilibrium is achieved, the temperature of the mixture is

A
100°C

B
55°C

C
75°C

D
0°C
Question 16
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?

A

B

C

D

Solution

First of all, there is a temperature rise from – 10°C to 0°C as the temperature of ice increases from A to B.
Then, at 0°C, the ice melts to form water at the same temperature. Thus, a straight line is drawn parallel to the horizontal axis from B to C.
Then, the water temperature rises from 0°C to 100°C from C to D.
Then, the water gets converted into steam at 100°C from D to E.
Question 17
1 / -0

The efficiency of a heat engine can never be

A
10%

B
20%

C
40%

D
100%

Solution

The efficiency of a heat engine can never be 100%.
Question 18
1 / -0

Conversion of heat into electrical energy can be achieved by

A
transistor

B
voltmeter

C
thermocouple

D
photoelectric cell

Solution

A thermoelectric device for measuring temperature, consisting of two wires of different metals connected at two points, a voltage being developed between the two junctions in proportion to the temperature difference. Hence, option (3) is correct.
Question 19
1 / -0

Vapour pressure of a liquid depends upon

A
quantity of heat

B
temperature of liquid

C
specific heat of liquid

D
density of liquid

Solution

Vapour pressure of a liquid depends upon the temperature of a liquid.
Question 20
1 / -0

If water at 0^oC, kept in a container with an open top, is placed in a large evacuated chamber,

A
all the water will vapourise

B
all the water will freeze

C
a part of the water will vapourise and the rest will freeze

D
ice, water and water vapours will be formed and reach equilibrium at the triple point

Solution

As the chamber is evacuated, the freezing point of water is lowered.
Due to its own internal energy, and coupled to the fact that there is vaccum, most of the water will evaporate away.
This will increase the pressure somewhat though by a negligible value.
Due to the high cohesion of water molecules, most of this vapour will freeze, releasing energy, thus melting ice or vapourising liquid water elsewhere.
Thus, ice, water and water vapour will be formed and reach equilibrium at the triple point.
Although nobody can be absolutely sure as to what will happen as this is a pure theoretical question because of the fact that neither have the conditions been specified nor can they be replicated.
However, this is the most logical and plausible answer and hence is correct.