Forms of Energy - Heat Energy (Thermal Energy)

Heat energy, also known as thermal energy. Heat energy is a type of energy that is transferred from a hotter object to a colder object. When heat is added to something, it makes that object warmer. For example, when you heat water on the stove, the water gets hotter because heat energy is being transferred to it.

• Heat is the energy that comes from the movement of tiny particles called atoms, ions, and molecules.
• These particles are always moving, and when they move faster, they produce more heat.
• Heat energy can move from one object to another if there is a temperature difference. This means heat always moves from high temperature to low temperature.
• Even very cold things, like ice cubes, still have some heat energy, but much less than hot objects like a stove or a volcano!

Methods of Heat Transfer: There are three main ways to transfer heat.

1. Conduction: Heat moves through solid objects. For example, if you leave a metal spoon in a hot cup of tea, the spoon will become hot because the heat from the tea is conducted through the metal.
2. Convection: Heat moves through liquids and gases. For example, in a room, hot air rises and cold air sinks, helping to warm up the space.
3. Radiation: Heat moves through empty space. This is how the sun’s heat reaches Earth, even though there’s no air in space to carry the heat.

A large amount of fossil fuel is burnt every day in power stations to heat water and produce steam, which further runs the turbine to generate electricity. Electricity transmission is more efficient than transporting coal or petroleum over the same distance. Therefore, many thermal power plants are set up near coal or oil fields. The term thermal power plant is used because fuel is burnt to produce heat energy, which is converted into electrical energy.

1. Sun: It is the most important source of heat energy for life on Earth. It warms the planet, allowing plants, animals, and humans to survive. 
2. Earth: The heat energy that is obtained from Earth is called geothermal energy.
3. Air: It is also an important source of heat energy.
4. Burning Fuels: Heat energy can be obtained by burning fuels like wood, coal, oil, or gas.
5. Electricity: Electric energy can be converted into heat energy.

Uses of Heat Energy:

• We use heat energy to cook food. 
• Heat energy is used in water heaters to provide hot water for bathing, cleaning, and cooking.
• During cold weather, we use heaters, radiators, or fireplaces to warm our homes. 
• Heat energy is used in electric irons to remove wrinkles from clothes.
• Factories use heat energy to melt metals, make glass, and produce materials like plastic and rubber.
• Power plants often use heat energy to generate electricity. They burn fuels like coal, oil, or natural gas to produce heat, which then drives turbines to create electricity.

To observe how a convex lens focuses sunlight to concentrate heat energy on a specific spot.

• Hold a convex lens over a sheet of paper in direct sunlight.
• Adjust the lens until a small, bright spot of light forms on the paper.
• Keep the lens steady for a few moments and observe what happens.
• The lens focuses sunlight into a tiny spot, concentrating heat energy.
• After some time, the paper may burn or develop a hole, showing that sunlight carries heat energy, which can be intensified using a convex lens.

Heat energy