Conduction of Heat
Conduction of Heat
Understanding how thermal energy transfers through materials without the material itself moving
Heat Transfer through SolidsWhat is Conduction?
Particle Vibration
Heat conduction occurs when vibrating particles pass their kinetic energy to neighboring particles.
Energy Transfer
Thermal energy moves from the hotter end to the colder end of an object.
Temperature Gradient
The greater the temperature difference, the faster the rate of conduction.
Key Concept
Conduction is the main method of heat transfer in solids. In metals, free electrons also help transfer heat very efficiently.
Particle Model of Conduction
How Heat Travels Through Materials
Cold End
Particles vibrate slowly
Heat Source →
Particles vibrate rapidly
Energy transfers from hot to cold as vibrating particles collide with their neighbors
Good vs Poor Conductors
Good Conductors
Materials that transfer heat quickly:
- Silver - Best conductor
- Copper - Used in pans
- Aluminum - Cooking foil
- Iron - Radiators
High Thermal Conductivity
Poor Conductors (Insulators)
Materials that transfer heat slowly:
- Wood - Handles
- Plastic - Coatings
- Glass - Windows
- Air - Trapped in insulation
Low Thermal Conductivity
Why are metals good conductors?
Metals have free electrons that can move through the metal and transfer kinetic energy quickly from the hot end to the cold end. This makes them much better conductors than non-metals.
Thermal Conductivity Values
| Material | Thermal Conductivity (W/mK) | Type | Common Use |
|---|---|---|---|
| Silver | 429 | Excellent Conductor | Electronics |
| Copper | 401 | Excellent Conductor | Cooking pans, wires |
| Aluminum | 237 | Good Conductor | Foil, pans |
| Iron | 80 | Moderate Conductor | Radiators |
| Glass | 0.8 | Poor Conductor | Windows |
| Wood | 0.15 | Insulator | Handles, furniture |
| Air | 0.024 | Excellent Insulator | Double glazing |
Higher values mean better conduction of heat
Interactive Conduction Experiment
See how different materials conduct heat at different rates:
Observations:
Factors Affecting Conduction
Temperature Difference
Greater temperature difference = faster heat transfer
Cross-sectional Area
Thicker materials conduct more heat
Length
Shorter distance = faster conduction
Material Type
Different materials have different conductivity
Time
Longer time = more heat transferred
Rate of conduction ∝ (Area × Temperature Difference) ÷ (Length × Material Resistance)
Real-World Applications
Cooking Pans
Copper or aluminum bases conduct heat quickly and evenly to food.
- Metal conducts heat from hob to food
- Wood/plastic handles are insulators
House Insulation
Materials like fiberglass trap air to reduce heat loss through walls and roofs.
- Loft insulation
- Cavity wall insulation
- Double glazing
Thermal Mugs
Vacuum flasks use a vacuum to prevent conduction and keep drinks hot or cold.
- Double-walled construction
- Vacuum prevents conduction
Heat Sinks
Metal fins on electronics conduct heat away from components to prevent overheating.
- Made of copper or aluminum
- Large surface area helps cooling
Insulation in Daily Life
Clothing
Trapped air between fibers insulates our bodies
Upholstery
Foam and fabric reduce heat loss
Double Glazing
Air gap between glass panes
Coolers
Expanded polystyrene keeps food cold
Pizza Boxes
Corrugated cardboard traps air
Safety Gear
Heat-resistant gloves for handling hot objects
Solved Examples
Example 1: Identifying Conductors
Question: Explain why a metal spoon in a hot drink becomes hot to touch, but a plastic spoon does not.
Example 2: Comparing Conductivity
Question: A copper rod and a glass rod of the same dimensions are heated at one end. After 2 minutes, the copper rod is hot along its entire length, but the glass rod is only hot at the heated end. Explain why.
Example 3: Practical Application
Question: A house has single-glazed windows. Suggest two ways to reduce heat loss through the windows and explain how they work.