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Conduction, convection and radiation

Energy can be transferred in three different ways - conduction, convection and radiation. All these ways are based on the particle theory.

The particle theory says that all forms of matter are made from small particles which are constantly moving around. Particle theory helps categorize the three main states of matter. In a state where particles are strongly attracted to each other, and are held tightly together in a state where they vibrate but remain relatively fixed, a solid exists. When there is some attraction between the particles, and they are held somewhat together, with a relatively-free degree of movement, a liquid exists. And when there is little attraction between the particles, and they can move freely around, a gas exists.

Liquids and gases are fluids. The particles in these fluids can move from place to place. Convection occurs when particles with a lot of heat energy in a liquid or gas move and take the place of particles with less heat energy. Heat energy is transferred from hot places to cooler places by convection.

Liquids and gases expand when they are heated. This is because the particles in liquids and gases move faster when they are heated than they do when they are cold. As a result, the particles take up more volume. This is because the gap between particles widens, while the particles themselves stay the same size.

The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, convection currents that transfer heat from place to place are set up.

1) The room heating., When the room is heating, the air is always moving so there’s warm in all room.

2) When we heat our hands near the fire or hot cup of tea, the heat is moved from the hot place to our body.

1) The edges of a refrigerator's doors have flexible seals to prevent cold air inside from mixing with hot air outside.

2) A vacuum flask is designed to prevent energy transfer between the content inside and its surrounding outside. With re-heating or cooling unnecessary, a vacuum flask is a convenient energy saving container.