Transmission of Heat Made Easy for JEE Students

 🌡️ Transmission of Heat – JEE Made Simple

Heat is a form of energy that flows from a hot object to a cold one. Just like water flows from high to low level, heat flows from higher temperature to lower temperature.

But how does heat move? There are three main ways heat is transferred:

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1️⃣ Conduction

🟢 Main Idea: Heat is transferred through solids without movement of particles.

📌 Examples:

Heating one end of a metal rod makes the other end hot.

Cooking using a steel pan.

💡 How It Happens:

When one part of a solid is heated, its particles vibrate more.

These particles pass their energy to neighboring particles.

🔍 Important Terms:

Good Conductors: Metal (Copper, Aluminium, etc.)

Bad Conductors (Insulators): Wood, Plastic, Air

🔥 Formula: Q=k.A(T¹-T²).T÷d

Where:

Q = heat transferred

 K= thermal conductivity

 A= area

 T¹-T²= temperature difference

 d= thickness

T = time

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2️⃣ Convection

🟢 Main Idea: Heat is transferred by the actual movement of particles in liquids and gases.

📌 Examples:

Boiling water (hot water rises, cold water sinks)

Sea breeze and land breeze

💡 How It Happens:

Hot fluids become lighter and rise.

Cold fluids come down to take their place.

This creates a circular motion called convection current.

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3️⃣ Radiation

🟢 Main Idea: Heat transfer without any medium.

📌 Examples:

Heat from the Sun reaching the Earth

Feeling warmth near a fire

💡 How It Happens:

Heat is transferred in the form of infrared waves.

It doesn’t need any material (solid, liquid, or gas) to travel.

🔍 Key Points:

Black surfaces absorb more radiation.

Shiny surfaces reflect radiation.

No particles move in this process.

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🎯 Important JEE Points:

✅ Conduction works best in solids.

✅ Convection happens in fluids (liquids and gases).

✅ Radiation works even in vacuum (like space).

✅ In conduction, only energy moves, not matter.

✅ In convection, matter also moves.

✅ Radiation is the fastest form of heat transfer.

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🔚 Summary Table:

Method Medium Needed Particle Movement Example

Conduction Solid No Metal rod heating

Convection Liquid/Gas Yes Boiling water

Radiation No No Sun heating Earth