Using Electromagnets 8-Nov-15 An electric current flowing through a wire produces a magnetic field – the higher the current the greater the magnetic field. Current Starter: Think about an electromagnet where there are coils of wire wrapped around an iron core. What will happen to the domains inside of the iron core when there are only a small number of coils? What will happen to the domains when there are more coils? Explain why the electromagnet is stronger when there are more coils. What happens to the domains when the current is switched off? MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY CREDIT MUST BE GIVEN IN FULL Caption Magnetic field round an electric wire. Iron filings (grey) being used to show the circular magnetic field associated with an electrical wire. The wire (brown) is running vertically down towards the paper on which the filings have been scattered. Magnetism is caused by the regular alignment of electrons within materials like metals, which explains why a regular flow of electrons (an electric current) produces the same phenomenon. 1 1

Using Electromagnets 8-Nov-15 You will have been successful in your learning when you are: Identified what makes a good conclusion and made improvements. Able to describe the factors that will affect how strong an electromagnet is Have applied your knowledge of electromagnets and magnetism to explain how an electric bell works

What needs doing today. A: If you have part of your homework missing (a yellow post it on your book) you will be doing it now. Graph paper is on the front desk. What you do not finish in 20 minutes you will do at lunchtime & I want it done properly! B: If you have your book back, look at your write up and make a comment as to how you can improve it. Analyse supplied conclusion & level using banding criteria Complete Electromagnets 1 and Electric bells sheet. Stick in picture of relay – explain how relay works. HOMEWORK – revise for test next lesson on Electrostatics, Logic gates, magnetism & Electromagnetism by producing a revision page (A4) using the summary sheet provided – I want to see everyone’s revision page. I will email a template to produce a revision page.

What is good about this conclusion A class investigated the effect of changing the current on the number of paper clips that the electromagnet picked up. Current (A) Number of paperclips picked up 2 3 4 6 10 8 12 What is good about this conclusion As the current increases the greater the number of paperclips picked up. This is because the electromagnet is getting stronger/more magnetic. I know this because when there is 2 Amps of current only 3 paperclips are picked up whereas when there are 8 Amps, 12 paperclips are picked up. This is because when there is more current the wire has a greater magnetic field which is able to cause a greater number of the domains to align in the iron core which increases the cores magnetism. When it is more magnetic then more paperclips can be picked up.

Conclusion Band What does this level look like? Foundation (3) States a pattern relating to graph Developing (4) Recognises simple patterns in own data/ numbers using an –er, -er statement Secure (5) Supports pattern with examples from the data Uses scientific terms to explain what is happening Identifies if certain results do not follow the pattern (anomalous or outliers) Confident (6) Attempts to use the correct scientific reasoning and terminology to explain the results. Identifies any anomalies Exceptional (7) Uses correct scientific reasoning and terminology to explain the results obtained Justifies the choice of anomalies

Now look over your own investigation homework Now look over your own investigation homework. Look at my comments and thinking about the work we have just done, spend 10 minutes improving your investigation using green pen.

Using electromagnets – relay Lifts, cars and other large electrical machines use high currents. A relay, which includes an electromagnet, is used to allow a small current in one circuit to control a large current in another circuit.

Using electromagnets – doorbell The circuit for a door bell includes an electromagnet. How does it work?

Complete the worksheet ‘Electromagnets and Electric Bells’ Collect different Key fact cards – use the key words to explain what the diagrams are showing

Use the revision checklist to produce a revision summary for the work we have covered this term – test next week