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© Boardworks Ltd 2003 KS4 Electricity – Static electricity.

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Presentation on theme: "© Boardworks Ltd 2003 KS4 Electricity – Static electricity."— Presentation transcript:

1 © Boardworks Ltd 2003 KS4 Electricity – Static electricity

2 © Boardworks Ltd 2003 A slide contains teacher’s notes wherever this icon is displayed - To access these notes go to ‘Notes Page View’ (PowerPoint 97) or ‘Normal View’ (PowerPoint 2000). Normal ViewNotes Page View Teacher’s Notes Flash Files A flash file has been embedded into the PowerPoint slide wherever this icon is displayed – These files are not editable.

3 © Boardworks Ltd 2003 Charge ParticleCharge Proton Neutron Electron +1 none

4 © Boardworks Ltd 2003 Charge, attraction and repulsion

5 © Boardworks Ltd 2003 Attraction and repulsion Positive and positive________ Negative and negative________ Positive and negative________ repel attract Like charges repel, unlike charges attract.

6 © Boardworks Ltd 2003 Charging objects What do we call the force you get when two materials rub together? Friction Let’s say you rub an insulator with a cloth, two things can happen: A.Electrons move from the cloth to the insulator. B. Electrons move from the insulator to the cloth. Let’s look at the two cases in more detail.

7 © Boardworks Ltd 2003 Electrons move from the insulator to the cloth Electrons move from the insulator to the cloth. The cloth becomes negatively charged. The insulator becomes positively charged. It is only the electrons that are free to move. What charge has the cloth? What charge has the insulator?

8 © Boardworks Ltd 2003

9 Electrons move from the cloth to the insulator Electrons move from the cloth to the insulator. The cloth becomes positively charged. The insulator becomes negatively charged. What charge has the cloth? What charge has the insulator? It is only the electrons that are free to move.

10 © Boardworks Ltd 2003 Identifying an unknown charge If you have a rod with an unknown charge you can identify the charge using two methods. If you bring it near a positively charged rod and it is attracted to the rod then the unknown charge must be ________. If you bring it near a positively charged rod and it is repelled by the rod then the unknown charge must be _________. negative positive OR

11 © Boardworks Ltd 2003 Identifying an unknown charge If the rod is a negative rod then…….. If you bring it near a negatively charged rod and it is attracted to the rod then the unknown charge must be ________. If you bring it near a negatively charged rod and it is repelled by the rod then the unknown charge must be _________. positive negative

12 © Boardworks Ltd 2003 Inducing a temporary charge If you bring a negatively charged rod near a piece of paper, why does the paper stick to the rod? The paper has no charge! As the rod approaches the paper, the electrons in the paper are repelled away from the rod. This makes one side of the paper negative and one side positive, a charge has been induced on the paper and the positive side of the paper is attracted to the negative rod.

13 © Boardworks Ltd If you bring a positively charged rod near a piece of paper, why does the paper stick to the rod? The paper has no charge! As the rod approaches the paper, the electrons in the paper are attracted towards the rod. This makes one side of the paper negative and one side positive, a charge has been induced on the paper and the negative side of the paper is attracted to the positive rod. Inducing a temporary charge

14 © Boardworks Ltd 2003 Uses of static electricity Uses of static electricity: 1._______________ 2._______________ 3._______________ 4._______________ Spray-painting Printers Photocopiers Pollutant-removers

15 © Boardworks Ltd 2003 A metal grid at a very high v______ runs down the middle of the chimney. E______ metal plates run down the inside of the chimney. Dirty smoke p______ become charged in the electric field. These charged particles are a______ to the earthed metal plates where they lose their charge and fall back down the chimney. Result – C____ smoke out of top of chimney. chimney wall earthed metal plate very high voltage on metal grid dirty smoke oltage arthed articles ttracted lean The electrostatic smoke precipitator

16 © Boardworks Ltd 2003 The spray gun is designed to produce tiny droplets of paint. The paint spray nozzle is connected to one terminal of an electrostatic generator. The other terminal is connected to the metal panel, which is earthed. As a result the charged droplets are attracted to the car body panel. This gives a uniform coating of paint. Also, the droplets travel along the lines of force of the field to reach hidden parts of the panel. The electrostatic paint spray

17 © Boardworks Ltd Paint gun nozzle has a positive charge Car is negatively charged + Spraying a car with paint The nozzle is connected to one terminal of an electrostatic generator. The other terminal is connected to the metal panel, which is earthed. Electrostatic generator

18 © Boardworks Ltd 2003 Fuel filling, paper rollers and grain shoots are all charge problems. As the fuel flows along the pipe or paper rolls over rollers or grain shoots out of tubes, static can build up. This can easily lead to a spark and then an explosion. To prevent this happening, the nozzles or rollers are made out of metal so any charge build up is conducted away. Large petrol tankers always have earthing straps between the tanker and the storage tank to prevent the risk of sparks. Dangers of Charge

19 © Boardworks Ltd 2003 underground tank or aeroplane tank. nozzle from tanker electrical link Transferring flammable liquids What prevents large static charges building up that could cause a possible explosion?

20 © Boardworks Ltd 2003 How is electrolysis used? Cu 2+ Anode is impure copper. This dissolves. Cathode starts as a thin piece of pure copper. MORE copper is deposited Sludge (impurities) Copper sulphate solution electrolyte AnodeAnode CathodeCathode Cu 2+ CathodeCathode AnodeAnode

21 © Boardworks Ltd 2003 Electrolysis Increase the current Increase the length of time the current flows Increase the resistance Increase the magnetic field Decrease the current x x x During electrolysis how can you increase the mass of material deposited at an electrode?

22 © Boardworks Ltd 2003 Charge, current and time We can express a relationship between charge, current and time mathematically using the equation: Charge = Current x time Q=It Charge measured in Coulombs (C) Current measured in Amps (A) Time measured in seconds (s)

23 © Boardworks Ltd 2003 Formula triangles Q I tt  x Formula triangles help you to rearrange formula, the triangle for Q=It is shown below: Whatever quantity you are trying to find cover it up and it will leave you with the calculation required. So if you were trying to find current, I….. …you would cover I up… …and you are left with the sum… I = Q t

24 © Boardworks Ltd 2003 A current of 6A flows for 3 minutes. How much charge flows? Q= It = 6A x (3x60)s = 1080 C In an examination you will not gain a mark for just writing Q=It. You must write out the whole formula: Charge = Current x time Always convert time to seconds!!!

25 © Boardworks Ltd 2003 Energy and charge We can express a relationship between charge, energy and potential difference mathematically using the equation: Energy = Charge x Voltage E=QV Charge measured in Coulombs (C) Energy measured in Joules (J) Voltage measured in Volts (V)

26 © Boardworks Ltd 2003 Formula triangles E Q VV  x Formula triangles help you to rearrange formula, the triangle for E=QV is shown below: Whatever quantity you are trying to find cover it up and it will leave you with the calculation required. So if you were trying to find charge, Q….. …you would cover Q up… …and you are left with the sum… Q = E V

27 © Boardworks Ltd 2003 Formula triangles

28 © Boardworks Ltd 2003 A charge of 100 C is delivered at a potential difference of 5V. How much energy is delivered? E= QV = 100 C x 5 V = 500 J In an examination you must always give the units. If you do not you will lose a mark. What is 500J in KJ? 0.5 kJ

29 © Boardworks Ltd 2003 What is the charge on an electron? A.Positive B.Negative C.Neutral D.Depends upon the atom

30 © Boardworks Ltd 2003 What force can be used to charge insulators? A.Gravity B.Friction C.Weight D.Energy

31 © Boardworks Ltd 2003 If a current of 6A is run through a device for 6 seconds. What charge is delivered to the device? A.1A B.36A C.1C D.36C

32 © Boardworks Ltd 2003 If a kettle has a 13A current and is on for 2 minutes, what charge is delivered to the kettle? A.26 C B.6.5 C C.1560 C D.0.23 C

33 © Boardworks Ltd 2003 If 6C of charge is delivered at a potential difference of 5V, how much energy is delivered? A.1.2 J B.11 J C.30 J D.30 kJ


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