Energy


 
 
Concept Explanation
 

Energy

Energy: The word ‘energy’ is used in many contexts, just like the word ‘work’ is. We hear people talk of a person’s energy, energy-giving tonics and drinks, solar energy, nuclear energy, energy from petrol, and so on. Energy is the ability to do work. The object which does the work, losses energy and the object on which work is done, gains energy.

The SI unit of energy is same as that of work i.e. Joule (J).

1 Joule of energy is required to do 1 J of work. Larger unit of energy is KJ.

1KJ = 10^3J.

Work done against a force is therefore stored as energy:

·      When a fast moving cricket ball hit a stationary wicket, the wicket is thrown away.

·      When a raised hammer falls on a nail placed on a piece of wood, it drives the nail into the wood.

Forms of energy: it exists in various forms like mechanical energy (sum of potential energy and kinetic energy), heat energy, chemical energy, electrical energy and light energy.

Mechanical Energy: The energy in a body may be by virtue of its motion(kinetic energy) or by the virtue of its position(potential energy). Energy in the body due to these conditions is called mechanical energy.

1. Kinetic energy :Energy possed by virtue of its motion is called kinetic energy. It is always positive and a scalar quantity.

2. Potential energy: It is the energy due to position. If a mass m  is at a height h above a lower level, the P.E. possed by the mass is (mg)(h). There are two common forms of energy gravitational energy and elastic energy.   

. Gravitational energy: When an object is allowed to fall from higher level to a lower level it gains speed duet o gravitational pull, i.e. it gains kinetic energy.

. Elastic energy:  This is due to the change in the shape of the body.Some work has to be done to change the shape of the body.

Sample Questions
(More Questions for each concept available in Login)
Question : 1

Identify  the kind of energy possessed by a running athlete.____________________.

Right Option : B
View Explanation
Explanation
Question : 2

A photocell converts  light energy into __________________

Right Option : B
View Explanation
Explanation
Question : 3

Energy cannot be measured in ________________

Right Option : A
View Explanation
Explanation
 
 


Students / Parents Reviews [10]