Electricity 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

Topic 7 page 1 4.I charged up a plastic comb by When I put the charged-up comb near some foil rubbing it with a duster/pulling it through my hair rubbing it with a duster/pulling it through my hair the foil jumped up to stick to the comb the foil jumped up to stick to the comb

Topic 7 page 2 Item Item What it was rubbed on Did the bits of foil move? Plastic combhair Plastic rulerhair Plastic bagcloth Wooden rulercloth Plastic pencloth Metal spatulacloth Text yes no yes no

Topic 7 page 3 The electroscope Stop!

Topic 7 page 4 Object Charged Object Charged Effect on Gold Leaf Plastic comb Plastic rod Plastic bag Plastic ruler 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.

Topic 7 page 6 Pulling and Pushing Pull together Charged object 1 Charged object 2 What happened? CombCling film Piece of record Polythene rod Perspex rod Pull together Push apart

Topic 7 page 6 Is there a pattern? Pull together Charged object 1 Charged object 2 What happened? CombCling film Piece of record Polythene rod Perspex rod Pull together Push apart same Push Push apart same same different Pull Pull together different different

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

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

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 Topic 7 page 7 two positive and negative remove negative charges add negative charges the negative charges are exactly balanced by the positive charges

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

Topic 7 page 10 1.A Van de Graff generator 2.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 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

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

Topic 7 page 12 Battery Ammeter A Bulb Switch

Topic 7 page 13 Part of circuit Statement 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

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

Topic 7 page 14 1.a) An electric circuit b) A complete circuit has 5. A B C D is a path that electricity can flow along is a path that electricity can flow along no gaps allowing electricity to flow along it no gaps allowing electricity to flow along it 0.2A0.5A0.65A0.95A

Topic 7 page 15 A A A.

A Topic 7 page 15 B. A

Topic 7 page 15 C. V V

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 Topic 7 page 17 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

0.2 Topic 7 page 18 X A A Y Z Current at XA Current at YA Current at ZA 0.2 A AA In a series circuit the current is the at all points in the circuit. same

0.2 Topic 7 page 19 X Y Z Current at XA Current at YA Current at ZA AAA In a parallel circuit the current taken from the battery the sum of the currents through the two bulbs equals

Topic 7 page 20 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 because Q3. Q4. House lights are better wired in parallel than series; a) b) B shares the current between two (dim) bulbs one of the bulbs is blown creating a break in the circuit don’t dim Broken bulb doesn’t put whole house into darkness

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

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

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

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

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

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

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

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

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

Topic 7 page 25 WireObservationUse Nichrome copper Tin-lead Glows red hot Conducts doesn’t get hot Heats up and melts Electric fire Conducting wires Safety fuse

Topic 7 page 26, 27 BatteryBattery voltage Bulb brightness V 6 V 12 V dim brighter bright When the voltage increases the current increases

Topic 7 page 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

Topic 7 page 29 Text Animation 1

Title: Aim: Method: Topic 7 page 30 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.

Topic 7 page 30 Diagram: Results: A bulb may be used instead of an ammeter A WireCurrent long short copper nichrome thick thin

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.

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

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.

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.

1.A long thin nichrome wire has a higher resistance because 2.a) Thick copper wires are good for carrying current because b) Long thin coils of nichrome are used in electric fires because Topic 7 page 35 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

Topic 7 page 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. the resistance wire is lengthened, causing a reduction in the current. because they use much more current than lamps because they use much more current than lamps

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

Circuit Symbols (components used in slides) V A You can find more downloads and help at