it is very easy to learn and understand

2. CHAPTER 8
By Tim SD

3. 8.1 GENERATION OF ELECTRICAL
CURRENT
• A generator is a device that converts
mechanical energy into electrical energy.
• Energy sources such as fossil fuel , running
water and nuclear fuels
• some alternative sources of energy are solar
energy and biomass fuel.

4. 8.2 TRANSFORMER
•A transformer is a device that can change the
voltage of alternating current by having
different number of turns in the primary and
secondary coins.
•The two types of transformers are step up
transformers and step down transformers.

5. 8.3 ELECTRICAL ENERGY TRANSMISSION
AND DISTRIBUTION SYSTEM
•Typical electrical power transmission and
distribution system
Power station – step up transformer –national
grid network – switch zone –step down
transformer – main substation – branch
substation – consumer.

6. 8.4 ELECTRICAL ENERGY SUPPLY AND
WIRING SYSTEM IN HOMES
The consumer unit has a main switch , circuit
breakers and fuses
Part of their function
. Furse box = protect a house circuit from
damage overloading,
Main switch = control the amount of current
through the circuit.

7. Circuit = breaks the circuit by springing out or
tripping its switch when the current flowing through
it exceeds .
•Live wire = carries current at a voltage of 240v
from the local to homes.
•Neutral wire = returns the current from house
•Earth wire connects an appliance directly to
earthed.
•Electric meter = record the amount of electrical
energy that has been used.

8. Type of wire international colour
code
Live brown
neutral blue
earth Yellow with green stripes

9. 8.5 COST OF USE ELECTRICAL ENERGY
• Electrical power P is defined as the rate at which
electrical energy is converted into energy.
• The s.1 unit of power is the watt (w) .
• Electrical energy = power x time .
• A commonly used unit for electrical energy is the
kilowatt- hour.

10. 8.6FUNCTIONS OF FUSE AND EARTH
WIRE
•A fuse is a short thin piece of wire which
becomes hots and melts when the current
flowing through it is a greater than rating of
the fuse.
•A short circuit is an electrical circuit which has
a very low resistance and carries very large
current.

11. •An earth wire connect the metal casing of an
electrical appliances directly to the earth.

12. 8.7 THE IMPORTANCE IN USE OF
ELECTRICAL
•Electrical accidents are electric shocks , and
electric fires.
•A miniature circuit beaker breaks a circuit
when its exceeds rating.
•An earth leakage circuit breaker turns off the
electrical when its exceeds 30 ma

13. 8.8 CONSERVING ELECTRICAL ENERGY
•Conserving electrical energy can prevent a
shortage of electrical energy.
•Energy labelling of appliance that describe
the capacity of an electrical appliance
improve efficiency.