1. ELECTRICITY AND MAGNETISM

2. CIRCUIT AND COMPONENTS BY: Tanisha Alexander BY: Tanisha Alexander 5A 5A

3. CIRCUIT DIAGRAMS Cell: supplies d.c. Dry cells may be rechargeable or non-rechargeable. Wet cells are rechargeable. Cell: supplies d.c. Dry cells may be rechargeable or non-rechargeable. Wet cells are rechargeable. D.c supply D.c supply a.c supply a.c supply

4. CIRCUIT DIAGRAMS Switch- opens and closes electric and electronic circuits. Fixed resistor- resistors control current flow in electric circuits

5. CIRCUIT DIAGRAMS Variable Resistor- also called a rheostat and is used to maintain a steady value of current. Variable Resistor- also called a rheostat and is used to maintain a steady value of current. Filament lamp- sometimes used as a current detector. Consists of an evacuated glass envelope and a thin filament. Filament lamp- sometimes used as a current detector. Consists of an evacuated glass envelope and a thin filament.

6. CIRCUIT DIAGRAMS Ammeter- a current measuring device placed in series with the component. Ammeter- a current measuring device placed in series with the component. Voltmeter- a device for measuring potential difference and is placed in parallel with the component. Voltmeter- a device for measuring potential difference and is placed in parallel with the component.

7. CIRCUIT DIAGRAMS Fuse- protects wires, parts of circuits or whole circuits from damage by excessive currents. Fuses are placed in the live wire of a.c. circuits. Fuse- protects wires, parts of circuits or whole circuits from damage by excessive currents. Fuses are placed in the live wire of a.c. circuits. Earth- this connection protects users of electrical equipment from electrical shocks caused by stray currents. Earth- this connection protects users of electrical equipment from electrical shocks caused by stray currents.

8. CIRCUIT DIAGRAMS Junction- wires are actually connected Junction- wires are actually connected Conductors crossing- wires cross but do not touch Conductors crossing- wires cross but do not touch

9. CIRCUIT DIAGRAMS Semiconductor diode- allows electron flow in one direction only. Used to change a.c to d.c i.e. in rectification. Semiconductor diode- allows electron flow in one direction only. Used to change a.c to d.c i.e. in rectification. Battery of cells- a series combination of identical cells Battery of cells- a series combination of identical cells

10. CELLS THE DRY CELL THE DRY CELL The common dry cell has a zinc outer case which serves as the negative terminal. A central carbon rod is the positive terminal. Ammonium Chloride in the form of jelly is the electrolyte. The dry cell also contains a mixture of powdered carbon and manganese dioxide. The carbon improves conduction, the manganese dioxide reduces polarization. Polarization is the process by which hydrogen atoms build up around the positive terminal of the cell or battery. Polarization reduces both the potential difference and the current that the cell can provide. The common dry cell has a zinc outer case which serves as the negative terminal. A central carbon rod is the positive terminal. Ammonium Chloride in the form of jelly is the electrolyte. The dry cell also contains a mixture of powdered carbon and manganese dioxide. The carbon improves conduction, the manganese dioxide reduces polarization. Polarization is the process by which hydrogen atoms build up around the positive terminal of the cell or battery. Polarization reduces both the potential difference and the current that the cell can provide.

11. THE PRIMARY CELL In a primary cell, the reactions cannot be reversed. In a primary cell, the reactions cannot be reversed. Primary cells cannot be recharged. Primary cells cannot be recharged. Example: A Dry Cell Example: A Dry Cell

12. THE SECONDARY CELL In secondary cells, the reactions can be reversed, therefore they can be recharged again and again. In secondary cells, the reactions can be reversed, therefore they can be recharged again and again. Example: The Lead-acid Battery Example: The Lead-acid Battery THE LEAD- ACID BATTERY: THE LEAD- ACID BATTERY: The lead-acid battery has a negative plate made of soft lead. It normally looks grey. The positive plat is made of lead dioxide which is red and the electrolyte is sulphuric acid. When a battery is in use or being discharged, both the negative and positive plates are converted to lead sulphate. The lead-acid battery has a negative plate made of soft lead. It normally looks grey. The positive plat is made of lead dioxide which is red and the electrolyte is sulphuric acid. When a battery is in use or being discharged, both the negative and positive plates are converted to lead sulphate.

13. DIFFERENCE BETWEEN A PRIMARY CELL AND A SECONDARY CELL PRIMARY CELL PRIMARY CELL Primary cells are cheaper to produce Primary cells are cheaper to produce Primary cells are easier to install Primary cells are easier to install Primary cells have higher internal resistance, thus they cannot supply large currents without being damaged Primary cells have higher internal resistance, thus they cannot supply large currents without being damaged SECONDARY CELL Secondary cells are more expensive to produce Secondary cells are harder to install Secondary cells have lower internal resistance, thus they can supply large currents without getting damaged.

14. RECHARGING A LEAD-AID BATTERY The following points should be noted carefully: The following points should be noted carefully: The positive end of the d.c. supply is joined to the positive end of the battery. The positive end of the d.c. supply is joined to the positive end of the battery. Low charging currents should be used Low charging currents should be used he variable resistor is used to control the current. he variable resistor is used to control the current.

15. CIRCUIT DIAGRAM TO SHOW HOW THE LEAD-ACID BATTERY CAN BE RECHARGED Circuit diagram: Circuit diagram:

16. QUIZ 1) Draw the symbols for a fixed resistor, a battery, a voltmeter and a fuse. 1) Draw the symbols for a fixed resistor, a battery, a voltmeter and a fuse. 2) List and the describe the components of a zinc carbon dry cell 2) List and the describe the components of a zinc carbon dry cell 3) Distinguish between a primary cell and a secondary cell and give an example of each. 3) Distinguish between a primary cell and a secondary cell and give an example of each. 4)Give three points that should be noted when recharging a lead- acid battery. 4)Give three points that should be noted when recharging a lead- acid battery. 5)Draw a circuit diagram to show how a lead-acid battery can be recharged. 5)Draw a circuit diagram to show how a lead-acid battery can be recharged.

17. THANK YOU FOR VIEWING. Drawings were made by Tanisha Alexander and not by a website.