Electricity. Part 1: Static Electricity

Transcription

1 Electricity Part 1: Static Electricity

2 Introduction: Atoms Atoms are made up of charged particles. Atoms are made of 3 subatomic particles: Electrons protons, electrons and neutrons. Protons () Charge () Charge Neutrons No Charge

3 Introduction: Atoms Normally, the number of protons () equals the number of electrons () and there is no Electrons charge. Protons () Charge If there are more protons () than electrons () () Charge the material will have a positive charge. Neutrons If there are less protons () than electrons () the material will have a negative charge. () Charge

4 Moving Charges Electrons can leave their atoms. Electrons can easily move, but protons cannot. When a material loses its electrons, it develops a () charge When a material gains electrons, it develops a () charge

5 Moving Charges Electrons can leave their atoms. Electrons can easily move, but protons cannot. This causes uncharged When a material loses its objects to become electrons, it develops a () () and () charged charge When a material gains electrons, We say the materials have it develops a () charge developed a static charge

6 Static Charge When two charged objects are placed near each other, they exert a force on each other. If objects have different charges, they attract. If objects have the same charge, they repel.

7 Static Charge Objects can be statically charged in 3 ways: Charging By Friction When two objects rub together, one object loses electrons and the other gains electrons. Positive negative

8 Static Charge Objects can be statically charged in 3 ways: Charging By Contact When a charged object touches a neutral object, the () charges move by direct contact. negative

9 Static Charge Objects can be statically charged in 3 ways: Charging By Induction When () charges separate without contact and are then pulled away from an object. Positive

10 Static Charge Charging by contact explains why you get shocked when you touch a metal object. This When When creates you you walk a touch build across a up the conductor, of excess carpet, like electrons, you a cause metal electrons doorknob, giving your to the shoes move electrons from and jump the your carpet body over to an to the overall the rubber metal, () soles giving of charge. you your a shock! shoes.

11 Lightning Lightning is simply a large scale version of what happens when you get shocked by a doorknob.

12 Lightning 1 In a cloud, there are () and () charges. There are equal numbers of each.

13 Lightning 2 Wind and gravity separate the charges, with the heavier () charges going to the bottom.

14 Lightning 3 Due to induction, the () charges in the cloud repel the () charges in the ground to move down.

15 Lightning 4 Now the ground has a () charge. The () charges in the ground attract the () charges in the cloud.

16 Lightning 5 When the difference is big enough, the () charges move from cloud to ground, causing lightning!

17 Lightning 6

18 Any Questions?

19 Electricity Part 2: Current Electricity

20 Circuit Electricity In this unit, we will cover: 1) What Is Current? 2) Electrical Circuits 3) Types of Circuits 4) Current 5) Voltage

21 Introduction Static electricity cannot make TVs and light bulbs work. This is because static electricity only carries a very limited amount of electric charge. To be useful, we need a constant flow of electric charges This flow is called electric current

22 Current Electric current is the flow of electrons through a conductor, such as a wire. The electrons come from a source like an electric cell, or a battery.

23 Current The electrons leave the cell at the negative () terminal

24 Current The electrons get pushed through the wires along a path

25 Current The electrons then return to the cell at the positive () terminal

26 Current While they flow around the wire, they transfer energy to things

27 Electric Circuits Electric current is the flow of electrons through a conductor, such as a wire. In order for charges to flow, there must be a closed path, or loop. This path is called an electric circuit

28 Open and Closed Circuits can either be open or closed: Open Closed No continuous path: electrons can t flow Continuous path: electrons can flow

29 Electric Circuits All circuits have certain basic components: Switch Device(s) Cell Wires

30 Drawing Circuits We draw electrical circuits using simple diagrams. Circuit Diagram

31 Circuit Diagrams Circuit diagrams are used to represent the parts of a circuit in a simple way. Circuit Symbols

32 Types of Circuits There are 2 major types of simple circuits: Series Circuit Only 1 path for the current to take. Each device is wired on a single path.

33 Types of Circuits There are 2 major types of simple circuits: ADVANTAGES Series Circuit Simple to build DISADVANTAGES If one device stops working, they all do

34 Types of Circuits There are 2 major types of simple circuits: Parallel Circuit More than 1 path for the current to take. Each device has its own connection to the cell.

35 Types of Circuits There are 2 major types of simple circuits: Parallel Circuit ADVANTAGES If one device stops working, the others stay working DISADVANTAGES Complicated to build

36 Current Electrons flow through electrical circuits. Current is the amount of electric charge that flows through a circuit in a given time. Series Current is measured in amperes (amps) Current is measured with a device called an ammeter

37 Changing Current The current changes depending on the number of cells The current changes depending on the number of components

38 Current In A Series Circuit? A 4 A? A In a series circuit, the current is the same every place in the circuit!

39 Current In A Parallel Circuit 6 A? A? A? A? A In a parallel circuit, the current is the splits up between the different loops

40 Summary: Current Series Circuit Parallel Circuit 6A 6A 6A 6A 2A 2A 2A Only 1 path Current stays same Multiple paths Current splits up

41 Voltage Electrons can only flow if they have energy. Voltage is a measure of how much energy each electron has in a circuit. Parallel Voltage is measured in volts (V) Voltage is measured with a device called a voltmeter

42 Changing Voltage The voltage changes depending on the number of cells The voltage changes depending on the number of components

43 Voltage In A Series Circuit 6 V V The 3 bulbs are the same? 2 V V V

44 Voltage In Parallel Circuit 6 V V? 6 V V? 6 V

45 Summary: Voltage Series Circuit Parallel Circuit 6A 6V 6A 3V 6A 3V 6A 2A 2A 2A 6V 6V 6V 6V Current stays same Voltage splits up Current splits up Voltage stays same

46 Any Questions?