Heat Energy

Heat Energy

Most of us refer the word ‘heat’ to anything that feels warm but scientifically, heat is defined as the flow of energy from a warm to cooler object.

Heat energy is all around us such as in icebergs, volcanoes and our body. Every matter has heat energy.

The result of the movement of minute particles known as atoms, molecules or ions in liquids, solids and gases is nothing but heat energy. Heat energy can be transferred by one substance to another and the flow because of the temperature difference between two objects is known as heat.

Ways Of Transferring Heat Energy

Convection transfers heat energy via air and liquids. The particles move apart and become less dense as air heats up and hence causes air to rise. While cooler air moves in from below and heats up.

Radiation warms the air using heat waves that radiate out of the hot object in all directions until absorbed by other object. Transfer of heat by radiation takes place at the speed of light and travels great distances.

Conduction transfers heat through one object to another when in direct contact. The travelling molecules of a warm object can increase the energy of the molecules in a cooler object. Solids conduct heat better than gases and liquids since particles are close together.

Particles In Collision

Particles have higher energy at higher temperatures. Some amount of this energy can be transmitted to other particles which are at lower temperature. For instance, when a fast travelling particle collides with a slower particle in the gas state, it transfers its energy to the other particle and thus increases the speed of slow moving particle.

When billions of particles collide with each other, a region of high energy transfers across the material until a condition of thermal equilibrium is developed, ie. the temperature across the material is is same.

Heat Energy Examples

An ice cube has some heat energy and also a glass of lemonade. If you put the ice in lemonade(warmer), the lemonade will transfer some of its heat energy to ice. Put differently, the ice melts and the water and lemonade will be of same temperature. This is nothing but reaching a state of equilibrium.

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Practise This Question

A hoop of radius r and mass m rotating with an angular velocity ω0 is placed on a rough horizontal surface. The initial velocity of the centre of the hoop is zero. What will be the velocity of the centre of the hoop when it ceases to slip?