Heat and Temperature

Question 1

What is zeroth law of thermodynamics

Answer 1

Zeroth law of thermodynamics states that “If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.

Question 1

What is the UFP and LFP of reumer scale?

Answer 1

UFP - 80
LFP - 0

Question 2

What will be the volume of gas at absolute zero? why?

Answer 2

Since V ∝ T , The ideal gas at absolute zero will have zero volume.

Question 3

For any scale, what is the constant value?

Answer 3

(T- LFP) / (UFP-LFP) is constant for any thermometer.

Question 4

What is thermal expansion?

Answer 4

Increasing the dimension (L , A , V)
on heating is thermal expansion.

Question 5

What is LFP and UFP for Rankine scale?

Answer 5

LFP- 492
UFP - 672

Question 6

If temp changes from °C to °F the specific heat will increase or decrease? Why?

Answer 6

Since s = (Q m/dt) and Δ1°C = 1.8 °F

Question 7

Range of Alcohol and Mercury thermometer are?

Answer 7

Alcohol : 78°C- -114°C
Mercury : 39°C - 357°C

Question 8

Why is absolute zero not zero energy temperature?

Answer 8

The KE ceases but there is PE due to mutual force of attraction between the molecules which is not zero.

Question 9

What is internal energy?

Answer 9

The total KE and PE of molecules or atoms of a substance is its internal energy.

Question 10

Why does temperature increase on heating?

Answer 10

Temperature is a measure of the average kinetic energy of the particles in a substance. When you heat a substance, the energy from the heat source increases the kinetic energy of its particles, causing the temperature to rise.

Question 11

Is it possible to measure the temperature of vacuum?

Answer 11

A perfect vacuum would have no temperature because it contains no particles

Question 12

Why the concept of temperature would be meaningless if zeroth law was not obeyed?

Answer 12

No Basis for Thermometers, inconsistent Temperature Definition, No Transitivity of Thermal Equilibrium

Question 13

What is linear expansivity?

Answer 13

The increase in length per unit length per unit degree rise in temperature is thermal expansivity.

Question 14

General formula for α, β ,γ is?

Answer 14

α, β ,γ = (Change in L,A,V)/ (Original L,A,V * Change in temperature)

Question 15

The ratio of alpha beta and gamma is?

Answer 15

α:β:γ = 1:2:3

Question 16

How is zeroth law foundation for temperature measurement?

Answer 16

• allows us to define and compare temperatures in a meaningful way.

The zeroth law states that:

If object A is in thermal equilibrium with object B, and object B is in thermal equilibrium with object C, then object A and object C are also in thermal equilibrium.
This means that if two objects have the same temperature, there will be no heat flow between them. Using this idea, we can measure temperature by comparing it to a reference object, like a thermometer.

Here’s how it works in simple terms:

A thermometer (object B) is placed in contact with another object (object A).
If there’s no heat flow between the thermometer and the object, they are in thermal equilibrium, meaning they have the same temperature.
We can then read the temperature from the thermometer because it tells us the temperature of both objects.
So, the zeroth law allows us to use a thermometer to measure temperature by ensuring that when two objects are at the same temperature, no heat is exchanged. This principle is the basis for all temperature measurement.

Question 17

Does potential energy increase the temperature of the substance?

Answer 17

Potential energy refers to stored energy, like when particles are separated by a distance or in a state that can release energy, such as in chemical bonds or gravitational fields. While potential energy can convert into kinetic energy (which can increase temperature), it doesn’t directly influence temperature unless this conversion happens.

Question 18

Is energy stored in rubber band and potential energy when particles are moved apart similar?

Answer 18

Yes, the way potential energy works when particles are moved apart is similar to how energy is stored in a stretched rubber band.

Question 19

What happens to time period of simple pendulum during summer or when temperature increases?

Answer 19

Since Δθ is positive the length of the pendulum increases also time period increases due to which the clock loses time and becomes slow.

i.e. it takes more time to complete one oscillation.

Question 20

What happens to time period of simple pendulum during winter or when temperature decreases?

Answer 20

Since Δθ is negative the length of the pendulum decreases also time period decreases due to which the clock gains time and becomes fast.

i.e. it takes less time to complete one oscillation.

Question 21

Linear expansivity of copper is 1.7*10^-5 °C^-1. What does it mean?

Answer 21

It means that when a copper of length 1m is heated and its temperature rises by 1° celsius then the increase in length is 1.7*10^-5 m. Its unit is °C^-1.

Question 22

What is isotropic solids?

Answer 22

Solids that expands uniformly in all directions when heated are isotropic solids.

Question 23

Small space is left between two rails on a railway track. Why?

Answer 23

Since rainway track is made up of metal and metals expand significantly when heated, on a hot day or due to friction, is not kept any gap, the rails would bend forcing an accident, due to which small space is left between two rails on rainway track.

Question 24

The value of cubical expansivity of mercury is 1.8 * 10^-5, what does it mean?

Answer 24

It means that, the increase in volume of a mercury having 1 m^3 density when temp is increased by 1 degrees is 1.8*10^-5