Energy can be briefly described as the ability to do work. Any form of energy can be utilized to do some kind of work. Energy can have various forms and all of them can be changed into another form.
Many of these types of energy can be converted into heat energy. These forms of energy are light, thermal, electrical, mechanical, nuclear etc. Basically, an increase in the amount of energy causes the system to heat up and decrease in the amount of energy causes it to cool down. Therefore, by doing some kind of work, we can feel our body becoming warmer. The various ways in which different forms of energy can be converted into heat energy are given below:
• Mechanical Energy: By doing some physical work, the mechanical energy is converted into heat energy. If a person exercises, his energy will be converted into heat by doing work, a part of which is visible as sweat. Also when a ball is dropped, a part of its kinetic energy is lost to heat the ball, due to which it bounces lower than it should have.
• Electrical Energy: Any electrical energy can be converted into heat energy by making use of electrical equipments like bulbs, hair dryers, stoves etc. The heat is produced when the conducting elements in these appliances get heated up due to the electric current flowing through them.
• Vibration Energy: When a person rubs his hands together, they become warmer. This is due to the fact that there are vibrations among the molecules which cause them to strike each other and their kinetic energy is converted into heat energy upon each collision.
• Nuclear Energy: Whenever a nuclear reaction takes place, a large amount of heat is dissipated. In fact, this heat energy is so severe that if it is not controlled, it can cause devastating effects. A very famous example of it is the nuclear bombing of Hiroshima and Nagasaki during World War 2.
• Light Energy: Light energy from the sun contains infra red radiations which cause objects to warm up. That is why we keep our clothes in the sun to dry. If this light is concentrated using a magnifying glass, the heat produced is so high that it can easily burn a piece of paper.
There are many other forms of energy that can be used to produce heat. The food that we eat has chemical energy stored in it and causes our body to become warmer due to the chemical reactions taking place in our body. All forms of energy including heat energy are expressed in Joules (SI unit). Another unit of heat is calorie.
1 Calorie = 4.184 Joules
Increase or decrease of temperature is often as a result of change in amounts of different forms of energy. For example, if the temperature of a room increases, it means that the kinetic energy of the air molecules has been increased. In case a person feels hot, it is because more heat energy has been transferred to his body and less internal heat is allowed to go out, raising the net temperature of the body.
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