Thermal Physics

Question 1

Boyle’s law

Pressure and volume relationship

Answer 1

pV = constant
p1 x V1 = p2 x V2

p1 and p2 are the two pressures in Pa
and V1 and V2 are the two volumes in m3

Question 2

Thermal Expansion (Linear)

Answer 2

change in L = a x Lo x change in temp.

Lo is the original length in meters
change in temp is in degrees Celsius
change in L (L1 - L0)
a is the linear expansivity of the material

Question 3

Charles’s Law:
Volume is directly proportional to
absolute temperature

Answer 3

V / T = constant
V1/T1 = V2/T2

V is the volume in m3
T is the temperature in Kelvin (K).

Question 4

Pressure Law:
Pressure of a gas is directly
proportional to the absolute
temperature

Answer 4

p / T = constant
p1/T1 = p2/T2

p is the pressure in Pa
T is the temperature in Kelvin (K)

Question 5

Gas law

pV / T = constant

Answer 5

p1V1/T1 = p2V2/T

In thermal physics the symbol θ is used
of Celsius scale and T is used for Kelvin
scale.

Question 6

Specific Heat Capacity

The amount of heat required to
raise the temperature of 1 kg mass
by 1 degrees C.

Answer 6

c = Q / m x Δθ.

c is the specific heat capacity in J/kg oC,
Q is the total heat in joules (J),
m is the mass in kg
Δθ is the change in temperature

Question 7

Thermal Capacity

amount of heat require to raise the temperature of a substance of any mass by 1 oC

Answer 7

Thermal capacity= m × c
Thermal capacity = Q / ∆θ

The unit of thermal capacity is J/oC.

Question 7

Thermal Capacity

amount of heat require to raise the temperature of a substance of any mass by 1 oC

Answer 7

Thermal capacity= m × c

Thermal capacity = Q / ߠ∆

Question 8

Specific latent heat of fusion

from Ice to liquid

Answer 8

Lf = Q/m

Lf is the specific latent heat of fusion in
J/kg or J/g,
Q is the total heat in joules (J),
m is the mass of liquid change from ice
in kg or g.

Question 9

Specific latent heat of vaporization

from liquid to vapour

Answer 9

Lv = Q/m

Lv is the specific latent heat of
vaporization in J/kg or J/g,
Q is the total heat in joules (J),
m is the mass of vapour change from
liquid in kg or g.

Question 10

Thermal or heat transfer

Answer 10

In solid = conduction
In liquid and gas = convection and also convection current
In vacuum = radiation

Question 11

Emitters and Radiators

Answer 11

Dull black surface = good emitter, good radiator, bad reflector
Bright shiny surface = poor emitter, poor radiator, good reflector