2019/2020 THIRD TERM BASIC TECHNOLOGY FOR JUNIOR SECONDARY SCHOOL 1 (LESSON 1)

CONCEPT OF ENERGY AND POWER
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Mechanical work is done when a force is applied to a body causing the body to move through a distance. The amount of work that is done is measured or calculated as the product of force, F, and the distance, d, moved through by the force.
That is Work = force x distance
The unit of work is the joule (J). This is defined as the work done when a force of one Newton moves through a distance of one metre.

Energy is the capacity to do work. A tank of air stored under pressure has energy, for when the air is released through a pneumatic hammer, it can perform work. An elevated block has the capacity to do work and is therefore said to have potential energy. Similarly, a coiled watch spring has energy since it is able to run the watch for an entire day. Water stored behind a dam has energy and may be used to operate turbines to generate electricity. The units of work and energy are thus the same. It is important to note that stored energy must be released to do work and these illustrates the principle of conservation of energy.

The Principle of conservation of energy states that energy can neither be created nor destroyed but can be converted from one form to another. Thus, the electric generator does not create electrical energy. It only converts mechanical energy into electrical energy. So also the electrical energy supplied to an electric lamp is not destroyed, it is only converted into light and heat energy. Also, When we burn coal or kerosine the chemical energy in the coal or kerosine is change into heat energy. The heat energy, may also be changed into electrical energy, for example in a disel generator. In all these cases, the principle of conservation of energy is upheld.

Power is the rate of doing work. Power is measured in watt (w).

If a boy takes 10 seconds to lift a 20kg box up a height of 6m, it then means that the rate of doing the work is calculated as follows: 

Time taken = 10 seconds
Consider the unit (seconds) used in the example mentioned above.

Rate of doing work = Power = (Force x Distance)/Time

Force = mass x acceleration = 20 x 10 = 200N
Power = (200 x 6)/10 = 120J/s or 120w 

MEASURING ENERGY
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Units are the identification of measurement. When a measurement is done and the value is written without a unit, it will be difficult to interpret the value and use it for further calculations.

We use an energy meter to measure electrical energy (what we commonly call PHCN meter). It measures the amount of energy consumed in a building. It measures  in kJ which is one thousand joules (1000J). 

INTRODUCTION TO FORMS OF ENERGY
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The major types of energy are:
1) Electrical Energy
2) Mechanical Energy
3) Chemical Energy
4) Heat Energy
5) Light Energy/Solar Energy
6) Nuclear Energy
7) Sound Energy


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