Meaning of Energy

Energy is defined as the ability or capacity to do work. The unit of energy is Joules (J)

Sources of Energy

There are two main sources of energy, the natural and the artificial sources of energy.

  1. The natural sources of energy are:
  2. Sun
  3. Food
  4. Natural gas
  5. Coal
  6. Wind
  7. Crude oil
  8. Wood
  9. Water
  10. The artificial sources of energy are:
  11. Batteries
  12. Electrical generator
  13. Petroleum products (e.g. diesel, kerosene etc.)

Forms of Energy

  1. Light energy
  2. Sound energy
  3. Heat energy
  4. Chemical energy
  5. Electrical energy
  6. Mechanical energy (potential and kinetic energy)

Transformation of Energy

Energy can be converted or transformed from one form to another. This is governed by the law of conservation of energy. The law of conservation of energy states that, energy can neither be created nor destroyed but can be converted from one form to the other.

Examples of energy conversion includes

  1. Electrical energy to heat energy – pressing iron, boiling ring, etc.
  2. Electrical energy to light energy – bulb, television, etc.
  3. Chemical to electrical energy – battery, etc.
  4. Electrical to kinetic energy – fan,
  5. Electrical to sound energy – electric bell, telephone ear piece, etc.
  6. Mechanical to light energy – bicycle dynamo
  7. Sound to electrical energy to sound energy – telephone

Uses of Energy

The following are some of the uses of energy

  1. Walking
  2. Cooking
  3. Playing
  4. Operating appliances
  5. Running
  6. Household work


  1. Define energy?
  2. Mention five forms of energy



  1. The energy conversion in phone is ….. (a) sound – electrical – sound (b) electrical – sound – sound (c) sound – electrical – electrical (d) electrical – electrical – sound
  2. The bicycle dynamo converts ….. energy to ….. energy (a) electrical – chemical (b) electrical – light (c) light – mechanical (d) mechanical – light
  3. Energy is the …….. to do work (a) power (b) ability (c) vision (d) hope
  4. The following are artificial sources of energy except ….. (a) wood (b) batteries (c) electrical generator (d) petroleum product
  5. The foods we eat contain which form energy? (a) chemical energy (b) mechanical energy (c) kinetic energy (d) potential energy


  1. State the law of conservation of energy
  2. Highlight four uses of energy
  3. Mention four devices and the energy conversion in their usage

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