What is Electricity? 1
  • This is a series circuit, showing how a torch is connected.

  • Televisions, washing machines and torches all use electrical energy.
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Electric Current 2
  • When we open the switch, the lamp goes out!

  • An electric current must move through the wire to make the lamp glow.
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Types of Energy 3
  • Electricity is a form of energy. Remember:

  • Energy cannot be created or destroyed, it can only be changed from one form to another.
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Stored Energy 4
  • Chemical energy is stored in food, fuels and in electrical cells.

  • A battery is made up of two or more electrical cells joined together.
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Conductors 5
  • We use metal wires to connect circuits .
  • Metals are good conductors of electricity.

  • Electricity moves through conductors.

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Insulators 6
  • Some materials don't let electricity pass through them.

  • These are electrical insulators.

  • Plastic, rubber and wood are all good electrical insulators.
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Components 7
  • The wires must be connected to both sides of components, like these lamps and motors.

  • The electricity goes through them
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Light Energy 8

  • A lamp changes electrical energy into light (and heat) energy in a circuit .

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Kinetic Energy 9

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Series Circuit 10
  • In a series circuit, if one lamp breaks then all of the lamps go out!

  • The electricity can't go through any of these lamps.

  • The circuit is broken.
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Static Electricity 11
  • Some clothes crackle, when you pull them off.

  • The clothes rubbing together make tiny electrical charges jump between your clothes.
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Current 13
  • When tiny electrical charges move in the wire of a circuit it is called a current.

  • For an electric current to move we need a complete circuit.

  • We also need something to push the current round.
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Electrons 14

  • The chemical energy in a battery pushes these tiny electrical charges round the circuit.

  • The tiny charges in the wires are called electrons.
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Ammeter 15
  • The current in a circuit is measured using an ammeter.

  • The ammeter tells us how many charges are moving through a circuit.

  • Current is measured in amperes (Amps for short) and we give it the symbol I.
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Losing Energy 16
  • Voltage tells us how much energy the electrons in the wire gain or lose across a component.

  • Electrons gain energy across batteries.

  • Electrons lose energy across components like lamps and motors.
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Voltage 17
  • The voltage in a circuit is measured using a voltmeter.

  • The voltage tells us how much energy the electrons have before and after a component.

  • Voltage is measured in volts. We use the symbol V.
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Resistance 18
  • Resistance tells us how hard it is for electrons to move through components in a circuit.

  • When electrons move through components with high resistance, like a lamp, they lose a lot of their energy.
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Changing Energy 19
  • Resistance is measured in Ohms Ω. We use the symbol R.

  • When electrons move through the lamp some of their energy is lost as light energy and heat energy.
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Work It Out! 20
  • We can use equations to calculate voltage, current and resistance.

  • If we know that the Current is 4 amps, and the Resistance is 2 ohms, then

  • Voltage = Current X Resistance

  • Voltage = 4 X 2

  • Voltage = 8V
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Use a Triangle 21
  • There are three equations, one to work out voltage, one for current and one for resistance.

  • We can use a triangle to remember them.
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Current 23
  • Current = Voltage / Resistance
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Resistance 24

  • Resistance = Voltage / Current
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Let's recap? 25
  • A circuit must be complete with no breaks.

  • The chemical energy in a battery pushes the charges (electrons) round the circuit.
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Let's recap? 26
  • Voltage tells us how much energy the electrons in the wire gain or lose across a component.

  • The movement of electrons through the circuit is called an electric current.
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Transforming Energy 27
  • The electrical energy in a circuit can be changed (transferred) as heat energy, light energy and kinetic energy by components.

  • Components with high resistance, slow the flow of current.
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Definitions: Voltage 28
  • You need to know these definitions.

  • Voltage (V) tells us how much energy the electrons, in the wire, gain or lose across a component.

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Definitions: Current 29
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Definitions: Resistance 30
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Using Symbols 31
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Using Symbols 32
  • Wires are made of metal, they are full of the tiny charges that we call electrons.
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The Wire 33
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The Cell 34
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Batteries 35
  • Cells and batteries only push in one direction. When you join them together, they must always point in the same direction.

  • The positive end of one battery connects to the negative end of the next battery.
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Switches 36
  • Switches are used to break a circuit.

  • If the switch is open, the battery cannot push electrons round the circuit.

  • The current stops flowing!

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Lamps (Bulbs) 37
  • As electrons are pushed through, energy is transformed to light, and heat-energy.

  • Lamps have high resistance.

  • It is hard for the battery to push electrons through the lamp.
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Motors 38
  • As electrical energy moves through a motor, it is transformed to kinetic energy (movement energy).

  • Swap the terminals on the battery, the motor will spin the other way!
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Resistors 39
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Resistors 40
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Variable Resistors 41
  • With some resistors we can change their resistance. These are called variable resistors.
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Variable Resistors 42
  • Big Resistance = Small Current

  • and...

  • Small Resistance = Big Current
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Circuits in Action 43
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Circuits in Action 44
  • The wires link the circuit.

  • Electrons in the wire are pushed by the battery.

  • The lamp transforms electrical energy to light and heat energy.
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Switches 45
  • When the switch is closed, the lamp lights up straight away! Don't Forget!

  • The wire is full of electrons. The electrons don't come from the battery. They are in the wire. The battery just pushes them.
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More Voltage 46
  • More batteries = more push

  • More push = higher voltage

  • Higher voltage = more energy

  • More energy = brighter lamp!
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Transformation 47
  • Lamps transfer electrical energy.

  • To light and heat Energy.

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Transformation 48
  • If you put more lamps into a series circuit, the electrical energy is shared out between them.

  • There is less energy for each lamp.

  • The lamps are dimmer.
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Voltage in Circuits 49
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Voltage in Circuits 50
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Voltage in circuit 51
  • The voltmeter tells us how much energy the electrons have gained from the battery (9.0 Volts in the diagram).

  • The Voltmeter (by the lamps) tell us how much energy the electrons lose at each lamp (4.5 Volts).

  • Don't forget:

  • Voltmeters must be connected to each side of a component.

  • The voltmeter is connected 'in parallel'.
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Flat battery 52
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Currents in Circuits 53
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Currents in Circuits 54
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Resistance in Circuits 55
  • Resistance = Voltage / Current

  • Resistance = 4.5 / 0.5

  • Resistance = 9 Ω
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Parallel Circuits 56
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Parallel Circuits 57
  • Parallel circuits are made up of two or more loops.

  • Each loop is a complete circuit.

  • Each circuit can work on its own.
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Parallel Circuits 58
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Parallel Circuits 59

  • If one lamp breaks all the current flows through the other lamp.

  • Parallel circuits are used in Christmas tree lights. If one lamp goes out, the others stay on.
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Parallel Circuits 60
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Fuses 61
  • Inside a fuse there is a piece of wire.
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  • If the current gets too high, the wire gets hot and melts. The circuit is broken.

  • We say the fuse has blown!

  • The fuse rating should always be higher than the current in a circuit.
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Hazards 62
  • Fuses protect us. They stop appliances getting damaged.

  • Different types of fuses can carry different amounts of current.

  • Common fuse ratings are: 1A, 3A, 5A and 13A.
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Household Electricity 63
  • Household electric circuits are 230V.

  • An electric shock from 50 volts can kill.

  • Water is a conductor of electricity.

  • Never let electrical equipment get wet!

  • Remember: Our nerves are electrical conductors.
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Our Nervous System 64
  • An electric shock can stop our heart beating and stop us breathing.

  • An electric shock can also restart our heart.

  • An electric shock can make muscles twitch!
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Electric Current 65
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Types of Energy 66
  • Electricity is a form of energy. Remember:

  • Energy cannot be created or destroyed, it can only be changed from one form to another.
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