Conservation of Energy


 
 
Concept Explanation
 

Conservation of Energy

Conservation of Energy

Energy can neither be created nor destroyed. It can only be changed from one form to another.

The above principle is called the principle of conservation of energy. It means that when all forms of energy are taken into account, the total energy in the universe remains constant. The principle is also valid for an isolated, i.e., one on which no force acts from outside.

Examples: 

1. When a ball is dropped from a height, its gravitational potential energy decreases, since its height decreases. It may seem that energy has been lost. But the ball gains speed, and hence, it acquires kinetic energy. Actually, as the ball falls its potential energy is gradually converted into kinetic energy.

2. When we switch on an electric torch, the chemical energy stored in the batteries is converted into heat energy as the filament of the bulb gets heated. Heat energy is then converted into light energy.

3. When a person does work on an object, the energy of the object increases. As the total energy is constant, the person must lose the same amount of energy. That is why when we push a heavy box on a surface, we feel tired. We do work on the box, and hence, lose energy.

Sample Questions
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Question : 1

___________________ can only be changed from one form to another.

Right Option : D
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Question : 2

The total energy of a swinging pendulum at any instant of time ______________________

Right Option : C
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Question : 3

Which of the following are correct :

(a) Energy can neither be created nor destroyed. It can only be changed from one form to another.

(b) When we switch on an electric torch, the chemical energy stored in the batteries is converted into heat energy.

Right Option : C
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