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30/04/2015 Static electricity and Electricity. Static electricity Lesson 1 30/04/2015.

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Presentation on theme: "30/04/2015 Static electricity and Electricity. Static electricity Lesson 1 30/04/2015."— Presentation transcript:

1 30/04/2015 Static electricity and Electricity

2 Static electricity Lesson 1 30/04/2015

3 Lesson 1+ 2 aims Static electricity Examples and uses of static electricity Electricity Circuits Voltage and current 30/04/2015

4 Static electricity Lesson 1 30/04/2015

5 Static electricity 30/04/ When two different insulating materials are rubbed together they become electrically charged. 2.Negative charges (electrons) rub off one material onto the other. The material which gains negative charges becomes negatively charged. The material which loses negative charges becomes positively charged.

6 Static Electricity

7 Only electrons move Both positive and negative charges are produced by the movement of electrons Positive charges do not move A positive static charge is caused by electrons moving away 30/04/2015

8 Static Electricity

9 Practical 1 Blow a balloon up, tie end up. Rub balloon on jumper or top Stick to wall 30/04/2015

10 Practical 2 Rub plastic strips with various cloths See which one produces static electricity Try balloon and plastic strips near water 30/04/2015

11 Repel or attract 30/04/ Electrically charged objects can attract small objects 2.Two positively charged objects will repel 3.Two negatively charged objects will repel 4.A positively charged object and a negatively charged object will attract

12 Like charges repel

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14 Opposite charges attract

15 Static Electricity

16 Practical 3 Van de Graaff 30/04/2015

17 Use and examples 30/04/ Static electricity can be used in photocopiers, smoke precipitator, and spray painting 2.A charged object can be discharged by connecting it to earth with a conductor 3.Static electricity can be dangerous (e.g. lightning). If the voltage becomes too great the negative charges can jump a gap causing a spark. This spark could ignite a flammable liquid nearby.

18 Electrostatic Precipitator Electrostatic precipitator

19 Static Electricity Static electricity

20 Static Electricity Static electricity

21 Quiz Quiz

22 Lesson 2 Electricity Circuits Current Voltage Resistance 30/04/2015

23 Circuit Symbols Circuit symbols

24 Switches - series circuit Switches – series circuit

25 Switches - parallel circuit

26 Conduction in metals 30/04/ Metals are good conductors of electricity because they have delocalised electrons which can carry the current.

27 Conduction in Metals Conduction in metals

28 1.Ionic compounds conduct electricity when molten or dissolved in water. The current is carried by charged particles called ions. 2.The positive ions (cations) attract to the negative electrode (cathode) 3.The negative ions (anions) attract to the positive electrode (anode) 4.At the electrodes the ions can lose their charge and form new substances. 5.This process is called electrolysis Conduction in liquids

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30 Electric current 30/04/ Electric Current is the flow of charge 2.Current can be measured using an ammeter (connected in series) 3.Current is measured in Amps (A) 4.Increasing the Voltage will increase the current 5.Increasing the Resistance will decrease the current

31 Current in a Series Circuit

32 30/04/2015 Current in a series circuit If the current here is 2 amps… The current here will be… And the current here will be… In other words, the current in a series circuit is THE SAME at any point

33 30/04/2015 Current in a parallel circuit A PARALLEL circuit is one where the current has a “choice of routes” Here comes the current… And the rest will go down here… Half of the current will go down here (assuming the bulbs are the same)…

34 Current in circuits 1.In a series circuit the current is the same everywhere 2.In a parallel circuit the current divides on entering a junction and rejoins on returning to the battery 30/04/2015

35 Current in a Series Circuit

36 Voltage or P.D 30/04/ Potential Difference is connected to the amount of energy that is gained or lost across part of a circuit 2.Potential Difference is measured using a Voltmeter (connected in parallel) 3.Potential Difference is measured in Volts (V) 4.Potential Difference gained across a cell or battery is called Voltage

37 30/04/2015 Voltage in a series circuit V VV If the voltage across the battery is 6V… …and these bulbs are all identical… …what will the voltage across each bulb be? 2V

38 30/04/2015 Voltage in a series circuit V V If the voltage across the battery is 6V… …what will the voltage across two bulbs be? 4V

39 30/04/2015 Voltage in a parallel circuit If the voltage across the batteries is 4V… What is the voltage here? And here? VV 4V

40 P.D in circuits 1.In a series circuit the potential difference is shared between the components 2.In a parallel circuit the potential difference is the same across each component and equals the voltage across the battery 30/04/2015

41 Summary In a SERIES circuit: Current is THE SAME at any point Voltage SPLITS UP over each component In a PARALLEL circuit: Current SPLITS UP down each “strand” Voltage is THE SAME across each”strand”

42 30/04/2015 An example question: V1V1 V2V2 6V 3A A1A1 A2A2 V3V3 A3A3

43 Answer voltage V1-3v V2-3v V3-3v current A1-1.5A A2-1.5A A3-3A 30/04/2015

44 Advantages of parallel circuits… There are two main reasons why parallel circuits are used more commonly than series circuits: 1)Extra appliances (like bulbs) can be added without affecting the output of the others 2)If one appliance breaks it won’t affect the others either

45 30/04/2015 Georg Simon Ohm Resistance Resistance is anything that will RESIST a current. It is measured in Ohms, a unit named after me. The resistance of a component can be calculated using Ohm’s Law: Resistance = Voltage (in V) (in  )Current (in A) V RI

46 Resistance in circuits Series – total resistance is equal to sum of all individual resistances (R=R 1 +R 2 ) Parallel-1/R = 1/R 1 +1/R 2 etc 30/04/2015

47 Calculate Q1. 1V, 1A calculate resistance Q2. Resistance =5 ohms, I = 2.5A V=? Q3.V=1.5V, Resistance=10ohms, I=? 30/04/2015

48 answers 1ohm 12.5V 0.15A 30/04/2015

49 Resistance Resistance

50 Lesson 3 I-V graphs Conductors 30/04/2015

51 Series Circuit – 1 bulb

52 Series circuit – 2 bulbs Series circuits – 2 bulbs

53 Parallel Circuit

54 Ohmic conductors R is constant Provided temperature is constant, current is directly proportional to the potential difference across it. 30/04/2015

55 I-V for ohmic conductor 30/04/2015

56 Graphs 1.Current-Voltage graphs can be used to show how the current flowing through a component changes with different voltages 2.The current through a resistor is directly proportional to the voltage across the resistor (at a constant temperature)

57 Comparing I-V graphs 30/04/2015

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59 explanation 1.The resistance of a filament lamp increases as the filament gets hotter 2.A diode allows current to flow in one direction only (the diode has a very high resistance in the opposite direction) 3.The resistance of a light dependent resistor decreases with increasing light intensity 4.The resistance of a thermistor decreases with increasing temperature 30/04/2015

60 Resistance of Components

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62 Quiz Quiz


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