 × ## Heat can be transferred across different bodies in the following ways:

Conduction: Conduction is the transfer of heat energy between molecules of a substance due to collisions between its molecules. A hot body has molecules that are rapidly vibrating about their position. These vibrating molecules impart their energy to nearby molecules, which start to vibrate. This process continues till heat energy is transferred across the whole conductor. Note that the molecules only vibrate about their mean positions but do not travel across the conductor. Generally, solids make the best conductors. Transfer of heat
Convection: Convection involves heat transfer via the actual movement of hot molecules of a substance. Liquids and gasses undergo this process since their molecules can move from place to place. The hotter molecules rise towards the top while the colder ones tend to sit down, causing heat transfer.

Radiation: Radiation involves heat transfer without any medium. It occurs via the emission and absorption of electromagnetic waves, which are emitted from hot bodies. Generally, hot bodies emit EM waves in the infrared region but very hot bodies can emit in the visible or even ultraviolet region.

## Solved examples

1. Determine the amount of heat energy dissipated if 50 kg of water is cooled down from 800 ℃ to 500 ℃. The specific heat of water is We are given that, . The relation between heat and specific heat capacity is given by Q=mcT. In this example, the change in temperature, ΔT=(800℃-500℃)= -300 ℃, where the negative sign signifies heat loss. Hence, 2. How much heat energy is required to raise the temperature of 1 kg of iron from 150 to 500 . The specific heat of iron is Proceeding just as in the last example, we have:

## Summary

In this article, we developed an understanding of the concept of heat, its units, and conversion across units. Further, we analyzed how to solve numerical related to heat transfer using a few solved examples.

1. What are the uses of heat energy?

Heat is an inseparable part of our lives and we list a few applications below:

1. Thermal power plants utilize heat energy to generate electricity.

2. Heat therapy is used to aid in pain relief.

3. Automobiles make use of heat energy generated by burning petrol and diesel.

4. We cook our food using heat.

2. How are heat and temperature related to each other?

Temperature and heat are closely related. Temperature measures the average kinetic energy of molecules. And heat is the form of energy that gives rise to the vibration of molecules.

3. What is a calorimeter?

A calorimeter is used to measure how much energy is involved in a chemical reaction. It is based on the principle of conservation of energy.

4. What is the law of conservation of energy?

The law of conservation of energy states that energy in this universe can never appear or disappear out of nowhere. It can only be transferred across its different forms. It is also possible to create energy from the mass using Einstein’s mass-energy equivalence.

5. What is specific heat?

Specific heat of a substance refers to the amount of heat energy required to raise the temperature of one unit mass of that substance by one unit.

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