1. Chp 18 Electricity

2. What is Electricity? A form of energy
Used to make electrical appliances work

3. Electric Current It is the rate of flow of electrical charge.
The path that the current flows through is known as a circuit.

4. Electric Current

5. Drawing circuit diagrams
Battery
Switch
Light bulb
Resistor
Variable resistor/rheostat
Voltmeter
Ammeter

6. Potential Difference:
The potential difference across any two points is the amount of energy needed to move one unit charge of electricity from one point to the other.

7. Resistance Resistance of the object =
Potential difference across its ends
Current flowing through it

8. Effects of an Electric Current
Electrical energy can be transformed into other forms of energy to produce many effects

9. Heating Effect of a Current
Wire heats up as a current passes through it
Electrical energy is converted into heat energy
Heat produced depends on the resistance of the wire
Greater resistance, greater heat

10. Heating Effect of a Current
Heating appliances have coils of wires made of high resistance materials such as nichrome
Heating elements heat up when current passes through them
Heat produced is then used for ironing, toasting, cooking and drying

11. Heating Elements in Heating Appliance

12. Heating Appliances

13. Magnetic Effect of a Current
An iron rod placed inside a coil of wire has increased magnetic field when the current is switched on
When the current is switched off, the iron loses its magnetism
The set-up is known as an electromagnet

14. Magnetic Effect of a Current
Used in many applications
Gives a magnetic field that can be switched on and off when desired

15. Applications of the Magnetic Effect of Current
Giant electromagnet
Telephone
Electric motors

16. Chemical Effect of a Current
Liquids such as salt water, vinegar and copper sulphate solution allow electricity to pass through them
Liquids are known as electrolytes

17. Chemical Effect of a Current
Electrolysis: Chemical decomposition of an electrolyte by an electrical current
Electrodes: Two wires or plates through which current enters and leaves the electrolyte

18. Application of the Chemical Effect of Current
Electrolysis is used in electroplating
Flow of current causes a thin layer of metal to be deposited on the object to be electroplated
Electrolysis is also used in industries to extract metals such as aluminium and magnesium from their compounds

19. Applications of Electroplating

20. Lighting Effect of a Current
Heating effect of a current can also lead to the lighting effect
In a light bulb, the heat generated is so great that the coiled filament begins to glow and give out light

21. Miscellaneous http://www.pge.com/microsite/PGE_dgz/wires/resist.html