What is different about this magnet? 23 November 2012 Investigating Electromagnets What is different about this magnet? Starter: What is this picture showing? What is it called? Why is it useful in a car scrap yard?

Investigating Electromagnets 23 November 2012 Investigating Electromagnets Learning Objectives Describe the three methods of magnetising iron. (level 4) Describe how to make an electromagnet and list the factors that will affect how strong it is. (Level 5) Use the correct vocabulary to clearly explain how objects that use electromagnetic induction work (Level 6)

Making a magnet A piece of steel becomes permanently magnetized when placed near a magnet. It can be magnetized more strongly when it is stroked with a magnet when it is placed inside a coil of wire which has a current flowing through it. The magnetic domains become aligned

Making a magnet N N Iron Steel Iron loses its magnetism easily Both are magnetised Iron loses its magnetism easily Only the steel is permanently magnetised. – we say it is a hard magnetic material. The iron is called a soft magnetic material as the magnetism is temporary. Draw the magnetised and demagnetised iron bar into your books. Draw arrows on the iron bars to represent the domains.

Magnetism and Electric Currents An electric current flowing through a wire produces a magnetic field Copy the diagram Current 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. 5 5

Solenoids A coil of wire which has a current flowing through it is called a solenoid. A core of iron can make the magnetic field around the solenoid stronger. A solenoid’s magnetic field has the same shape as a bar magnet’s field. Credit: ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY CREDIT MUST BE GIVEN IN FULL Caption Magnetic field of a solenoid. Solenoid (centre) and iron filings (black) marking the field lines of its magnetic field. A solenoid is simply a coil of electrical wire. When electricity flows through the wire, a magnetic field is created. Any current flowing through a wire will have a magnetic field, but the coiling of a lot of wire produces a strong magnetic field like that of a bar magnet. This is a phenomenon known as electromagnetism, and the solenoid is known as an electromagnet. It can be used to magnetize materials like iron, and also to generate motion (as in an electric motor) and to generate electricity (as in a dynamo). 6 6

Making an Electromagnet When electricity is passed through a coil of wire, the coil has a magnetic field around it. This is called an electromagnet If the coil of wire is wrapped around a piece of iron, such as an iron nail, the magnetic field gets stronger.

Aim: To investigate some factors that affect the strength of an electromagnet Investigate the following two questions ‘how does the number of coils affects the number of paper clips attracted to an electromagnet?’ Use the 9 questions to help you write up your investigation in detail. You will be assessed on this write up.

1. Question 2. Hypothesis 3. Diagram 4. Method 5. Safety 6. Table 2. State what you think will happen and why, including any relevant Science 1. What question are you investigating? What are the independent, dependent and control variables? 3. Draw a diagram (Pencil and ruler used), with labels. 5. State what the potential hazards are and why it could be dangerous. Say how you have minimised to risk to yourself and others 4.Method: Needs to be bullet pointed/ numbered Needs to clearly say what you have done, what you have changed, measured, repeated etc. – make sure someone else could use this method to do the experiment. 1. Question 2. Hypothesis 3. Diagram 4. Method 5. Safety 6. Table 7. Graph 8. Conclusion 9. Evaluation 6. All Heading and UNITS included Any anomalous results highlighted and not included in average. Overall presentation (ruler and pencil used) 8. Conclusion: er/er statement. Use of data to exemplify trends. Discuss whether your data is good enough to draw a conclusion. Discussion of science to back up the trends observed. 7. Title Label and Units Independent on x axis Dependant on y axis Axis and sensible Scale Points plotted accurately Lines of best fit drawn 9. Mention any anomalies and why they might have arisen. How could your experiment be improved with reasons?