Thermodynamics Test

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Thermodynamics Test - 19

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Question 1
1 / -0

The temperature at the bottom of a high water fall is higher than that at the top because

A
by itself heat flows from higher to lower temperature

B
the difference in height causes a difference in pressure

C
thermal energy is transformed into mechanical energy

D
mechanical energy is transformed into thermal energy

Solution

The water at the top of the waterfall, falls and gains velocity.
The potential energy it has converts into kinetic energy.
When the water lands at the bottom, the kinetic energy converts into heat and hence the water is warmer at the bottom.
Question 2
1 / -0

In the equation $$PV^{\gamma}$$ = constant, the value of $$\gamma$$ is unity. Then the process is

A
isothermal

B
adiabatic

C
isobaric

D
irreversible

Solution

Given that:
$$PV^{\gamma} = constant$$
Given that $$\gamma = 1$$
$$PV = constant$$
For an ideal gas:
$$PV = nRT = constant$$
i.e.
$$nRT = constant$$
$$T = \dfrac{constant}{nR} = constant$$
Hence the process is isothermal.
Question 3
1 / -0

In changing the state of thermodynamics from A to B state, the heat required is $$Q$$ and the work done by the system is $$W$$. The change in its internal energy is

A
$$Q + W$$

B
$$Q - W$$

C
$$Q$$

D
$$\displaystyle{\frac{Q - W}{2}}$$

Solution

$$\Delta Q = \Delta U + \Delta W$$
$$\Rightarrow$$$$\Delta U = \Delta Q - \Delta W = Q - W$$ (Using proper sign)
Question 4
1 / -0

Thermodynamics is concerned in part with transformations between

A
different forms of heat energy

B
internal energy at various tempratures

C
one form of mechanical energy into other forms

D
heat, internal energy and mechanical work

Solution

The first law of thermodynamics gives us the relation between, heat supplied, internal energy and work done. Basically it talks about the interchangeability of energy (law of conservation of energy). It studies the relationship between heat temperature and energy.
Option D is correct.
Question 5
1 / -0

The thermodynamical variable temperatures is defined by:

A
zeroth law

B
I law

C
II law

D
III law

Solution

The thermodynamical variable temperatures is defined by: zeroth law of thermodynamics.
Question 6
1 / -0

When an inflated tyre bursts, air escaping out will

A
get heated up

B
be cooled

C
not undergo any change in its temeperature

D
be liquified

Solution

The correct answer is option(B).
The air inside the tube of a vehicle is under high pressure. When a puncture occurs to the tyre, air inside comes out from that high pressure to outside environment which is at low pressure. In this process, it has to travel through a small hole.
According to the principle of Joule-Thomson effect. This says that when a gas at high pressure moves to an area of low pressure via a small hole, the gas cools down.
Question 7
1 / -0

A thermos bottle containing coffee is vigorously shaken. If the coffee is considered as a system, then the temperature of the coffee will ____________.

A
increase slightly

B
fall

C
remain the same

D
data insufficient

Solution

Since the thermos bottle is vigorously shaken, the kinetic energy of molecules in the coffee will be increased. As the temperature is directly proportional to the average kinetic energy of the molecule, therefore temperature of the coffee will be increased.
Question 8
1 / -0

Joule's experiment converts

A
work into heat

B
work into electricity

C
heat into work

D
electricity into work

Solution

Joule's experiment converts work into heat

Accurate investigation of the relationship between heat developed and mechanical work spent was taken up by the British Scientist James Prescott Joule. The main aim of his investigations was to determine exactly the ratio between the work done and the quantity of heat produced.

Joule used different arrangements for doing the work, W in different ways and measured the corresponding amount of heat, H produced in each case. In all the cases he found that the expenditure of the same amount of work always produced the same amount of heat. Every time he found that 4186 joule of work was spent to produce the same amount of heat which could raise the temperature of one kg of water through 10C. He established the relation, W/H to be a constant quantity. The constant relation W/H was represented symbolically by the letter ‘J’. J is known as Joule's mechanical equivalent of heat. ‘Symbolically, we can write :

W/H = J or W = JH
Question 9
1 / -0

A thermos bottle containing coffee is vigorously shaken. If the coffee is considered as a system, then the temperature of the coffee will :

A
increase slightly

B
fall

C
remain the same

D
it cannot be determined

Solution

The correct answer is option(A).
Since the thermos bottle is vigorously shaken, the kinetic energy of molecules in the coffee will be increased. As the temperature is directly proportional to the average kinetic energy of the molecule, therefore temperature of the coffee will be increased.
Question 10
1 / -0

Which one of the following is not a thermodynamical co-ordinate?

A
$$V$$

B
$$R$$

C
$$T$$

D
$$P$$

Solution

$$R$$ is a constant term. To define a thermo dynamic state of a gas we use any two of three physical quantities $$P,V$$ and $$T$$. Following ratio is always constant
$$\cfrac{PV}{T}=R$$ (constant)
So, if we change $$P$$ and $$V, T$$ will automatically change itself to make ratio constant.

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Thermodynamics Test - 19

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Thermodynamics Test - 19

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SHARING IS CARING

Question 1

by itself heat flows from higher to lower temperature

the difference in height causes a difference in pressure

thermal energy is transformed into mechanical energy

mechanical energy is transformed into thermal energy

Solution

Question 2

isothermal

adiabatic

isobaric

irreversible

Solution

Question 3

$$Q + W$$

$$Q - W$$

$$Q$$

$$\displaystyle{\frac{Q - W}{2}}$$

Solution

Question 4

different forms of heat energy

internal energy at various tempratures

one form of mechanical energy into other forms

heat, internal energy and mechanical work

Solution

Question 5

zeroth law

I law

II law

III law

Solution

Question 6

get heated up

be cooled

not undergo any change in its temeperature

be liquified

Solution

Question 7

increase slightly

fall

remain the same

data insufficient

Solution

Question 8

work into heat

work into electricity

heat into work

electricity into work

Solution

Question 9

increase slightly

fall

remain the same

it cannot be determined

Solution

Question 10

$$V$$

$$R$$

$$T$$

$$P$$

Solution

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