• This is a series circuit, showing how a torch is connected.

• Televisions, washing machines and torches all use electrical energy.

• When we open the switch, the lamp goes out!

• An electric current must move through the wire to make the lamp glow.

• Electricity is a form of energy. Remember:

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

• Chemical energy is stored in food, fuels and in electrical cells.

• A battery is made up of two or more electrical cells joined together.

• We use metal wires to connect circuits .
• Metals are good conductors of electricity.

• Electricity moves through conductors.

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

• These are electrical insulators.

• Plastic, rubber and wood are all good electrical insulators.

• The wires must be connected to both sides of components, like these lamps and motors.

• The electricity goes through them

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

• 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.

• Some clothes crackle, when you pull them off.

• The clothes rubbing together make tiny electrical charges jump between your clothes.

• 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.

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

• The tiny charges in the wires are called electrons.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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

• There are three equations, one to work out voltage, one for current and one for resistance.

• We can use a triangle to remember them.

• Current = Voltage / Resistance

• Resistance = Voltage / Current

• A circuit must be complete with no breaks.

• The chemical energy in a battery pushes the charges (electrons) round the circuit.

• 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.

• 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.

• You need to know these definitions.

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

• Wires are made of metal, they are full of the tiny charges that we call electrons.

• 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.

• Switches are used to break a circuit.

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

• The current stops flowing!

• 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.

• 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!

• With some resistors we can change their resistance. These are called variable resistors.

• Big Resistance = Small Current

• and...

• Small Resistance = Big Current

• The wires link the circuit.

• Electrons in the wire are pushed by the battery.

• The lamp transforms electrical energy to light and heat energy.

• 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.

• More batteries = more push

• More push = higher voltage

• Higher voltage = more energy

• More energy = brighter lamp!

• Lamps transfer electrical energy.

• To light and heat Energy.

• 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.

• 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'.

• Resistance = Voltage / Current

• Resistance = 4.5 / 0.5

• Resistance = 9 Ω

• Parallel circuits are made up of two or more loops.

• Each loop is a complete circuit.

• Each circuit can work on its own.

• 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.

• 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.

• 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.

• 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.

• 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!