Heat and Thermodynamics
A complete physics website covering heat, temperature, thermal expansion, calorimetry, transfer of heat, gas laws, thermodynamics, laws of thermodynamics, heat engines, refrigerators, diagrams, formulas, solved examples, and exercises.
1. Heat
Heat is a form of energy that flows from a hotter body to a colder body.
2. Temperature
Temperature measures the degree of hotness or coldness of a body.
| Scale | Unit |
|---|---|
| Celsius | °C |
| Kelvin | K |
| Fahrenheit | °F |
3. Thermal Expansion
Most substances expand on heating and contract on cooling.
Types of Expansion
- Linear Expansion
- Area Expansion
- Volume Expansion
4. Transfer of Heat
Methods of Heat Transfer
| Method | Description |
|---|---|
| Conduction | Heat transfer without movement of particles |
| Convection | Heat transfer through movement of fluid |
| Radiation | Heat transfer without medium |
5. Calorimetry
Calorimetry is the measurement of heat exchanged.
Example
Find heat required to raise temperature of 2 kg water by 10°C.
Given:
m = 2 kg
c = 4200 J/kg°C
ΔT = 10°C
Q = 2 × 4200 × 10
Q = 84000 J
6. Thermodynamics
Thermodynamics deals with relation between heat and mechanical energy.
First Law of Thermodynamics
Heat supplied = Increase in internal energy + Work done.
Second Law of Thermodynamics
7. Heat Engine and Refrigerator
Heat Engine
A heat engine converts heat energy into mechanical work.
Refrigerator
A refrigerator transfers heat from low temperature to high temperature using external work.
8. Practice Exercises
Short Questions
- Define heat.
- What is temperature?
- Name methods of heat transfer.
- State first law of thermodynamics.
- What is calorimetry?
Numerical Problems
- Find heat needed to raise temperature of 5 kg water by 20°C.
- Convert 27°C into Kelvin.
- Calculate heat if m = 3 kg, c = 4200 J/kg°C and ΔT = 5°C.
9. Formula Summary
| Topic | Formula |
|---|---|
| Heat Energy | Q = mcΔT |
| Kelvin Conversion | K = °C + 273 |
| First Law | ΔQ = ΔU + W |