Brief information on heat and thermodynamics
In this particular article Brief information on Heat and thermodynamics, we are going to cover some most important topics of heat and thermodynamics. We will discuss heat and temperature, thermal expansion in detail and easiest way possible.
Heat and Temperature
- Heat is a form of energy. That is transferred between two bodies or between adjacent part of a body or between a system and its environment at different temperatures.
- When some heat is given to a body and its state does not change. Then the temple of the body rises and if heat is taken from a body its temperature falls. I.e., temperature can be regarded as the effect of cause, heat.
- Temperature is that property of a body which helps us yo decide the degree of its hotness.
- Zeroth law of thermodynamics: If two systems A and B are each in thermal equilibrium with some another system C. Then A and B will be in thermal equilibrium with each other.
- Scales of temperature: Centigrade or Celsius (° C), Fahrenheit (° F) and Kelvin (K), are commonly used temperature scales.
- Although the temperature of a body can be raised without limit, it cannot be lowered without limit and theoretically limiting low temperature is taken to be zero on the Kelvin scale.
- Mathematically, heat supplied to the body, or heat released by the body. ΔQ = msΔT. Where, m = mass of the body, s= specific heat of the body and ΔT = change in temperature
- The amount of heat required to change the state of a body of mass m from solid to liquid at melting point of the solid or from liquid to gas at boiling point of the liquid is ΔQ= mL, where L is the latent heat of the substance.
- As ΔQ= msΔT ⇒ s = ΔQ/ mΔT, if the substance undergoes the change of state which occurs at constant temperature (ΔT= 0), then s = ΔQ/0 = ∞. Thus the special heat of a substance when it melts or boils at constant temperature is infinite.
Thermal or heat capacity
The Thermal or heat capacity of a body, H= ms
- Thermal capacity of the body and its water equivalent are numerically equal.
- If thermal capacity of a body is expressed in terms of mass of water, it is called water equivalent of the body.
Heating curve of a body (state changes from solid to liquid and liquid to gas)
When two substances at different temperatures are mixed with each other then, the heat flows from higher temperature substance to the substance at lower temperature untill a common temperature is reached. In this process, heat lost by one substance = heat gained by the other substance.
Thermal Expansion in solids is of three types
1. Coefficient of linear expansion
α = increase in length/ original length× Rise in temperature
α = L- L / L × ΔT
Or L = L ( 1+ αΔT)
2. Coefficient of area expansion
β = Increase in area / Original area × Rise in temperature
β = A – A / A × ΔT
Or A = A ( 1+ βΔT)
3. Coefficient of volume expansion
γ = Increase in volume / Original volume × Rise in temperature
γ = V – V / V × ΔT
Or V = V ( 1+ γΔT)
The three coefficient of thermal expansion are related as α = β/ 2 = γ / 3
Effect of thermal expansion
- With increase in temperature volume of substance increase while mass remains constant, therefore density should decrease. ρ’ = ρ / 1+ γΔθ ≈ ρ ( 1- γΔθ)
- When a solid whose density is less than the density of liquid is floating, then a fraction of it remains, decrease or remains immersed. This fraction is ƒ = ρ/ ρ. When temperature is increased, ρ and ρ both will decrease. Hence, fraction may increase, decrease or remain same. At higher temperature, ƒ’ = ƒ (1+ γΔθ / 1+ γΔθ) Where Δθ= increase in temperature if γ > γ, then ƒ’ > ƒ or immersed fraction will increase.
- When a solid whose density is more than the density of liquid is immersed completely, then upthrust will act on 100% volume of solid and apparent weight appears less than the actual weight. Wapp = W – F. Here F = Vρg. With increase in temperature, V will increase and ρ will decrease, while g will remain unchanged. Therefore upthrust may increase, decrease or remain same.
- With increase in temperature, length of pendulum will decrease. Therefore time period will increase. A pendulum clock will become slow and it loses the time.
In this article Brief information on heat and thermodynamics, we have studied heat and temperature briefly. We have discussed about zeroth law of thermodynamics, scales of temperature, thermal and heat capacity of a body, heating curve, joule’s Thomson effect, tharmal expansion, effect of thermal expansion etc in detail and in easiest way possible.