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Conservation of Energy and Its Types

Grade 10
Jul 26, 2023


In this session, you are going to learn about the conservation of energy, efficiency, and why all the appliances around us are not a hundred percent efficient.

Types of Energy

We need the energy to do work. Energy is present in different forms:

  1. Heat energy
  2. Chemical energy
  3. Electrical energy
  4. Sound energy
  5. Light energy
  6. Atomic energy
  7. Nuclear energy
  8. Thermal energy

Transformation of Energy

The change of one form of energy to another form of energy is known as the transformation of energy.

This transformation of energy helps us in the utilization of energy as per our need, in the form we need the energy.

A few examples from daily life where the transformation of energy takes place are:


1. A flashlight converts chemical energy stored in a battery into light energy. 

Chemical to Light
Chemical to light

2. An engine of a vehicle converts chemical energy (petrol or diesel) into kinetic energy

Chemical to mechanical
Chemical to mechanical

3. Mechanical energy can be converted to electrical energy by generators, and in the reverse, the conversion of electrical energy to mechanical energy can be accomplished by motors.

Mechanical to electrical
Mechanical to electrical

4. Every living plant converts light energy, which they get from the sunlight, into chemical energy through photosynthesis. 

Radiation energy to chemical energy
Radiation energy to chemical energy

And a few more.


Law of Conservation of Energy

When energy changes from one form to another, the total amount of energy remains constant.

Energy can neither be created nor destroyed.

Although some energy may be wasted during conversion, the total energy of the system remains constant.

Energy is lost in the conversion in multiple ways.


  1. Tube light converts electrical energy to light energy; energy loss is in the form of heat energy.
  2. When an organism eats food, the chemical energy is converted into muscular energy, but most of it is lost in respiration, heart, and excretion.
Energy loss
Energy loss


The energy lost in the atmosphere during a conversion determines the efficiency of that particular appliance.

The efficiency of a machine describes the ability of a machine to convert the energy supplied into useful forms of energy.

We calculate the efficiency of a machine using the formula:

The efficiency of a machine is the useful energy transferred to the machine divided by the total energy supplied to the machine.

The efficiency of a machine has no unit.

We can increase the efficiency of a machine by reducing dissipative forces like frictional force, air resistance, and heat loss due to thermal radiation. Dissipative forces can be reduced by using lubricants and ball bearings, insulating the system using non-conducting walls, streamlining the machines, etc.

The formula used to calculate efficiency is:

Efficiency formula
Efficiency formula

Questions and Answers

Question 1: What is the efficiency of an object that converts mechanical energy into electrical energy if the input energy is 100 J and 30 J is lost as heat energy?


Input energy = 100J

Useful output energy = 70J

Efficiency = 70/100 = 0.70

Question 1: What is the form of the energy lost during the conversion of energy when you are eating food?


Muscular energy


  • When energy changes from one form to another, the total amount of energy remains constant.
  • Energy can neither be created nor destroyed.
  • some energy may be wasted during conversion, but the total energy of the system remains constant.
Energy Output
Energy Output
Conservation of Energy


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