Electricity

Introduction How do you think we can get an electric current? -We can do that by simply plugging something into the mains and switching on! Can we use that electricity for experiments? No, mains electricity is very dangerous!

A safe electric current We can use a battery or a cell to produce an electric current which is safe for us to use. Do you know the difference between a cell and a battery? A battery is simply 2 or more cells joined together

Problem: Mmm... so a torch needs two batteries to light up. I wonder how many batteries are needed to light up our house?!

Problem: We do not use batteries to light our house! We use mains electricity coming from power stations. Power stations work by the burning of fossil fuels.

How do we make a circuit? Will this circuit work?

No. This is called an open circuit. For current to flow we need a closed/complete circuit. If the circuit is broken there is no current and the bulb doesn’t light.

What can we use to control whether current passes or not? What do you do when you want to turn off the lights for example?

Using a switch You can use a switch to control whether you have an open or a closed circuit and therefore decide if current passes or not.

Symbols Activity and worksheet

Ammeter and current Current is a measure of how much electric charge flows through a circuit. The more charge that flows, the bigger the current Current can be large or small. It is measured by using an ammeter. Just as the mass of an object is measured in kilograms, the current in a circuit is measured in amps (in short, A).

Voltmeter and voltage Voltage is a measure of the difference in electrical energy between two parts of a circuit. The bigger the difference in energy, the bigger the voltage. In other words voltage represents the brightness (energy of the bulb) Voltage is measured in volts. The symbol for volts is V.

Resistor and resistance A resistor is something which provides resistance- limits the flow of current. In a variable resistor we can control the amount of resistance

Safety with electricity Worksheet

Safety with electricity Electricity can cause fires and injuries, even death. Here are some rules for using electricity safely: Do not put anything into an outlet except a plug. Do not pull on the cord to unplug an appliance, hold the plug and pull. Dry your hands before you plug in or unplug a cord. If a plug is broken or a cord is cut or worn, do not use it.

Never touch any power lines. Some power lines are buried underground. If you are digging and find a wire, do not touch it. Do not fly a kite or climb a tree near a power line. If there is an electrical storm (with lightning), turn off and disconnect electrical appliances, like the TV and computer. Do not plug too many cords into one outlet. Keep appliances away from water. Do not use a hair dryer if there is water nearby.

How to draw a circuit Circuits are drawn by using the particular symbols joined together by straight lines(wires):

Using circuit symbols to draw circuit diagrams Worksheet + Circuit boards

Series and Parallel circuits There are 2 kinds of circuits: Series circuits: if there are no branches then it's a series circuit Parallel circuits: if there are branches it's a parallel circuit

Series circuits What would happen if we increase the number of light bulbs in series circuit ? -Come and try out for yourselves! If you put more lamps into a series circuit, the lamps will be dimmer than before, because the voltage has to be divided between all of the bulbs.

Series circuits In a television series, you get several episodes, one after the other. A series circuit is similar. You get several components one after the other. If you follow the circuit diagram from one side of the cell to the other, you should pass through all the different components, one after the other, without any branches.

Parallel circuits In parallel circuits different components are connected on different branches of the wire. If you follow the circuit diagram from one side of the cell to the other, you can only pass through all the different components if you follow all the branches. We can think of a parallel circuit as more than one series circuits joined together!

Parallel circuits What would happen if we increase the number of light bulbs in a parallel circuit ? -Come and try out for yourselves! If you put more lamps into a parallel circuit, the lamps will be have the same brightness as before, because the voltage remains the same between all of the bulbs!

Series Circuit Advantages 1.Series circuits are useful if you want a warning that one of the components in the circuit has failed. 2. They also use less wiring than parallel circuits. Disadvantages 1.If anywhere in the circuit is opened (ex. a bulb explodes), the whole circuit will not work. 2.Bulbs connected in series are dimmer than if they are connected in parallel with the same battery voltage.

Parallel circuit Advantages 1.If a particular bulb is damaged, the rest of the circuit will still work. 2. The brightness of each bulb will not be affected by adding other bulbs. 3. You can choose what to switch on and off in the circuit. Disadvantages 1. You need more wiring.

Circuits-Where do we use them? Series Circuits? -Christmas tree lights Parallel circuits? -Light system in our houses

Ernie the Electrician has noticed that buying electrical wire for his work is becoming more and more expensive. He thinks he can invent a cheaper version and wants you to test some materials he’s thought of. He doesn’t know what the word means but apparently the materials need to be good “conductors”. I’ve got an idea! Your Challenge... £ £