Topic 7 - Electricity

1. Topic 7 - Electricity • Charges • Electrons • Voltage • Current • Series • Parallel • Resistance The slides are designed to tie in with a set of worksheets, but could be adapted or serve as a template for other teachers

2. Topic 7 page 1 rubbing it with a duster/pulling it through my hair • I charged up a plastic comb by • When I put the charged-up comb near some foil the foil jumped up to stick to the comb

3. Topic 7 page 2 yes yes yes no yes no Text

4. Topic 7 page 3 The electroscope Stop!

5. Topic 7 page 4 Rises up Rises up Rises up Rises up If an uncharged object is brought near an electroscope the gold leaf If a charged object is brought near an electroscope the gold leaf doesn’t move. rises up.

6. Topic 7 page 6 Pulling and Pushing Pull together Push apart Pull together Push apart Pull together Push apart

7. Topic 7 page 6 Is there a pattern? different Pull together Pull together same Push apart Push apart different Pull together Pull together same Push apart Push apart Pull together different Pull together same Push apart Push apart

8. Topic 7 page 6 5. If the charged objects are the same material then they will repel

9. The centre of the atom contains both yellow neutrons and green positive protons Around the outside are the negative electrons Topic 7 page 7 Where Does Charge Come From?

10. Topic 7 page 7 1. There are kinds of electrical charge called 2.a) To make an object positively charged you need to b) To make an object negatively charged you need to 3. If a substance is neutral it means that two positive and negative remove negative charges add negative charges the negative charges are exactly balanced by the positive charges

11. Topic 7 page 8 4. Two charged polythene rods will repel because 5. A cleaned mirror will be dusty within 24hrs because 6. A woolen jersey could be attracted to a nylon shirt because they have the same charge the charge attracts dust they would have opposite charges which would attract

12. A Van de Graff generator • a) Your hair stands on end when you • touch a Van de Graff generator • because • b) Your hair goes down when you touch a • water tap because Topic 7 page 10 builds up and stores a negative charge your hairs become negatively charged and repel each other the negative charges leave you flowing along the pipes to the ground and the hairs stop repelling

13. - - - - - - - - - - - Topic 7 page 11 moving current When a flows, charges are Now fill the blanks

14. A Topic 7 page12 Battery Switch Ammeter Bulb

15. Topic 7 page 13 Part of circuitStatement Battery measures current Bulb pushes the current Switch changes electrical energy to light Ammeter carries current round circuit Connecting wire turns the current on and off

16. Topic 7 page 14 Dim bulb Bright bulb – small current - large current The a bulb the bigger the brighter current

17. Topic 7 page 14 • a) An electric circuit • b) A complete circuit has • 5. A B C D is a path that electricity can flow along no gaps allowing electricity to flow along it 0.2A 0.5A 0.65A 0.95A

18. A A Topic 7 page15 A.

19. A A Topic 7 page15 B.

20. V V Topic 7 page15 C.

21. Topic 7 page 17 2a)The battery b) The wires c) The ammeter d) The switch 3a) The energy change in the bulb is b) The energy change in the battery is 4a) Electricians use symbols to pushes the current through the wires conduct the electricity measures the current opens and closes a gap Electrical energy  Light energy Chemical energy  Electrical energy make their diagrams clearer and tidier

22. A A A Topic 7 page 18 X 0.2 0.2 A Z Y 0.2 A 0.2 0.2 0.2 In a series circuit the current is the at all points in the circuit. same

23. A A A Topic 7 page 19 0.4 Z X 0.2 Y 0.2 In a parallel circuit the current taken from the battery the sum of the currents through the two bulbs 0.2 0.2 equals 0.4

24. Q1. The two bulbs in circuit B make less light than the one bulb in circuit A because Q2. No current flows in circuit C becauseQ3. Q4. House lights are better wired in parallel than series; a) b) Topic 7 page 20 B shares the current between two (dim) bulbs one of the bulbs is blown creating a break in the circuit Broken bulb doesn’t put whole house into darkness don’t dim

25. V A Using Voltmeters and Ammeters Voltmeter – connected in parallel Ammeter connected in series

26. V Correctly Wired? No! The voltmeter has been connected in series – it should be parallel

27. A Correctly Wired? No the Ammeter has been connected in parallel – it should have been series

28. A Correctly Wired? Yes! This Ammeter has been connected correctly in series

29. A Correctly Wired? Yes! This Ammeter has been connected correctly in series

30. V Correctly Wired? Yes! The Voltmeter has been connected correctly in parallel

31. A Correctly Wired? Yes! The Ammeter has been connected correctly in series

32. Effects of Series? As more bulbs are added in series the bulbs grow dimmer

33. Topic 7 page 23 Circuit Diagram Iron Plastic Brass Rubber Copper Perspex Steel Glass Graphite Wood

34. Topic 7 page 25 Electric fire Glows red hot Conducts doesn’t get hot Conducting wires Safety fuse Heats up and melts

35. Topic 7 page 26, 27 dim 1.5 V brighter 6 V 12 V bright When the voltage increases the current increases

36. Topic 7 page 28 5. Write down your ideas. • The more batteries the brighter the bulb • This holds true as long as the batteries face the same way • If batteries are reversed they cancel each other out Elephant handout

37. Topic 7 page 29 Text Animation 1

38. Topic 7 page 30 Title: Aim: Method: Choosing the best type of cable To compare copper/nichrome, thick/thin, long/short wires and find the best Test thick and thin wires in a circuit and measure how it affects the current using an ammeter. Then test copper/nichrome and long/short wires.

39. A Topic 7 page 30 Diagram: Results: A bulb may be used instead of an ammeter

40. Topic 7 page 30 Conclusion: • Short wires are better than long wires. • Copper wires are better than nichrome wires. • Thick wires are better than thin wires.

41. Topic 7 page 31 Copper has a resistance than nichrome Thin wires have resistance than thick ones Longer wires have resistance than short ones lower higher higher

42. Topic 7 page 32 The variable resistor 4. Write down what you found out. The longer the wire (coil) the dimmer the bulb, the shorter the wire the brighter the bulb.

43. Topic 7 page 33 The variable resistor Write down what you found out. The longer the wire (coil) the smaller the current and the dimmer the bulb. The longer wire has a higher resistance.

44. Topic 7 page 35 • A long thin nichrome wire has a higher resistance because • a) Thick copper wires are good for carrying current because • b) Long thin coils of nichrome are used in electric fires because thick has a lower resistance, as does copper and short wires. copper is a good conductor and thick wires have low resistance nichrome has a high resistance causing it to heat up without melting

45. Topic 7 page 35 3. A variable resistor is used to 4. When the volume on a radio is turned Down 5. Cookers need thick cabling increase and decrease the current by changing the length of a resistance wire the resistance wire is lengthened, causing a reduction in the current. because they use much more current than lamps

46. Topic 7 page 36 The purpose of a fuse is to protect you from a short circuit - safety Not to make the device work

47. V A Circuit Symbols(components used in slides) You can find more downloads and help at www.lab6.co.uk