Heat Transfer Through Conduction

Conduction is how heat moves through materials that are in direct contact.

Here's how it works: When you heat up a solid, the particles inside it start to vibrate. These heated particles then pass their energy to the cooler particles nearby.

The ability of a material to conduct heat varies, and it mostly depends on its properties, especially how well it can transfer heat, which is called thermal conductivity.

Important Ideas about Conduction:

1. Thermal Conductivity: This tells us how well a material conducts heat.

   It is measured in a unit called watts per meter per Kelvin (W/m·K).

   For example:

   • Metals like copper have high thermal conductivity, around 400 W/m·K.
   • Aluminum is also a good conductor with about 205 W/m·K.
   • On the other hand, materials like wood and rubber do not conduct heat well. Their thermal conductivity is low: about 0.13 W/m·K for wood and 0.2 W/m·K for rubber.

2. Temperature Gradient: Heat moves from hotter areas to cooler areas when conduction happens.

   You can figure out how much heat is being transferred using a rule called Fourier’s Law, which shows it like this:

   $Q = -k \cdot A \cdot \frac{\Delta T}{L}$

   Here’s what the symbols mean:

   • $Q$ = heat transfer (in joules)
   • $k$ = thermal conductivity (in W/m·K)
   • $A$ = area where heat is moving (in square meters, m²)
   • $\Delta T$ = difference in temperature (in Kelvin)
   • $L$ = thickness of the material (in meters)

3. Types of Materials:

   • Metals: They are great at conducting heat because their electrons move freely and quickly transfer energy.
   • Non-metals: Materials like plastics are not good conductors. Their electrons are tightly held, making energy transfer slow.

Real-Life Examples:

• Cooking on a metal pan is a good example of conduction. Heat from the stove travels through the metal and cooks the food.
• In buildings, insulating materials help keep heat inside, showing why it is important to use materials with low thermal conductivity for better energy efficiency.

In summary, conduction helps us understand how heat travels through different materials. It highlights the importance of thermal conductivity and how particles interact in various substances.