2. Generation of electricity• Chemical cells• Convert chemical energy to electrical energy• Zinc and Copper plate
3. Dry cells
4. Lithium ion, Nickel Cadmium cell
5. Lead acid accumulator• Car battery• Converts chemical energy to electrical energy• Rechargeable
6. Generation of Electricity• Bicycle Dynamo• Kinetic energy to electrical energy
7. Solar cell• Convert light energy to electrical energy
8. Electric Current• Caused by the flow of negative charges along a conductor
9. Why negative charges move?• Due to potential difference between 2 points of a conductor• Potential difference = Voltage Electrons move from region of Higher electron concentration to region of Lower electron concentration.
10. Make sure you can differentiate electric
11. How much negatively-charged electrons are moving along aconductor at a particular time?
12. What is current? • Flow of electrons along a conductor
13. How does electrons move along a conductor??
14. How to measure electric current?• Ammeter• Milliammeter• Connect in series (one by one)• Positive terminal ammeter – positive terminal battery• Negative terminal ammeter – negative terminal battery
15. Ammeter• Measures electric current• SI unit for current = Ampere (A)How to measure?? One after another – Series circuit
16. • The brighter the light bulb, the higher the reading of ammeter.
17. What are the differences between these circuits?
18. What is voltage?• Voltage is provided by the electrical sources• Eg. Battery, lead acid accumulator
19. Voltage• Potential difference across 2 points
20. Voltage• Measure potential difference (Voltage) between 2 points• SI unit – Volt (V)• How to connect?To measure voltage of a light bulb,we have to connect the voltmeter acrossthe light bulb – Parallel circuit
21. • The brighter the light bulb, the higher the reading of voltmeter.
22. Resistor• To restrict current flow• Used in - Radio, Television, Oven, Fan
23. Resistance reduces current flow
24. The greater the resistance the smaller the current flows
25. Electric circuit components
26. All materials haveelectrical resistanceResistance =Frictional forceOpposes the direction of current flowGood electrical conductor = Low resistancePoor electrical conductor = High resistance
27. Factors affecting resistance• The length of the wire – The longer the wire, the greater the resistance• The thickness of the wire – The thicker the wire, the lesser the resistance• The type of material used – Different types of materials have different resistances • Copper and Silver • Iron and Magnesium
28. Factors affecting resistance• The length of the wire – The longer the wire, the greater the resistance
29. Factors affecting resistance• The thickness of the wire – The thicker the wire, the lesser the resistance
30. • The thickness of the wire – The thicker the wire, the lesser the resistance
31. Factors affecting resistance• The type of material used – Different types of materials have different resistances
32. Relationship between current and resistance• High resistance >>>> _____ current• Low resistance >>>> _____ current Length of nichrome wire Ammeter reading 20 0.9 30 0.7 40 0.5 50 0.3 60 0.1
33. Relationship between voltage and current• Imagine voltage as battery• Higher voltage >>> Greater current• Lower voltage >>> Lesser current
34. ResistanceOhm’s law – Current (I) that flows through a metal conductor is directly proportional to the potential difference (voltage) across it, if resistance remains constant
35. Relationship betweenCurrent, Voltage and Resistance
36. Series and Parallel circuit• Series – One way traffic• Parallel – More than one way
37. • When more light bulbs are added, the brightness of light bulb decreases.
38. Advantages & Disadvantages of Series Circuit – One switch can switch off everything
39. Parallel circuit• Each bulb receive full voltage from battery and have same brightness
40. Advantages and disadvantages of Parallel circuit• Other electrical appliances can still function if one of them break down