Magnetism and levitation There is a great deal of science in magic. Although magical illusions such as levitation appear to break the laws of physics – they are actually simply using the laws of physics to their advantage, through deception. Magnets form a magnetic field around them. Magnetic fields consist of lines of force. Forces of magnetic attraction and repulsion move along these lines. Magnetic field lines can be seen by spreading iron fillings in a magnetic field. Like poles repel each other. Two North poles show repulsion lines as do two South poles. While North and South poles attract. Note the difference in field lines between repulsion and attraction. Magnetic lines of force have a number properties that you should know about. They include: They form closed loops from pole to pole that represent paths of least resistance. They never cross one another. They all have the same strength. The distance between them increases with increasing distance from the poles. . They flow from one pole, to the other . Using iron fillings we can see the magnetic field lines surrounding a strong magnet. Magicians can create magic by levitating objects using magnets. Pictured on the right is a very simple levitation trick involving circular magnets and 4 square magnets. When the magnets are properly aligned to repel each other levitation occurs. Magnets can not only produce strong attraction but also strong repulsion. What evidence do you see in the video that magnetic forces act over short distances? View the video on the right. The two magnets experience a force of attraction. This is obviously an interaction between north and south poles an interaction between two north poles an interaction between two south poles These magnets are obviously less powerful than the magnets shown above. Why? Constructing such a levitating toy is not difficult. A good design should deliver spectacular results. - block of wood 1 cm X 2cm X 60 cm - saw and screw driver - screws - two round magnets and 4 square magnets as shown on the right. - pencil. But the magician needs to have the upper hand. Levitation must happen on the magician's command. Repulsion with permanent magnets will not do. Electromagnets are what's needed. How do electromagnets work. Click for a detailed explanation. However, simply put, any time a current is forced to travel in loops a magnetic field is created as shown on the right. An electromagnet is a collection of these loops with an iron core, such as a nail, as shown on the right. Now when current flows through the looped wire it makes the nail magnetic. Using a switch of some description the magician can control the precise moment when the magnetic force is needed. When the switch is open, as shown on the right, we say that an open circuit is formed. This means that current can not flow from the battery, around the wire and back to the battery. Once the switch is closed current can flow and a magnetic field is created. At this point we say that the circuit is closed. Continue with an investigation with electromagnets 1) What is a magnetic field composed of? 2) How can forces of repulsion and attraction be achieved with magnetic fields? 3) What is the difference between a permanent magnet and an electromagnet? 4) Why do magicians prefer to use electromagnets? 5) Levitation is achieved by what type of forces? magnetic forces of repulsion magnetic forces of attraction anti-gravity forces electrostatic forces of repulsion 6) What is the difference between a closed circuit and an open circuit? 7) How is an electromagnet constructed? 8) Electricity flowing through a wire creates what type of force? 9) A circuit contains a battery, globe, switch and coils of wire wrapped around an iron nail. When the switch is turned on the light globe glows and the nail becomes magnetised. Draw a diagram of the circuit using the symbols on the right. Click to see an example of a circuit with a swirtch and an electromagnet. 10) What happens when the circuit is open? magnetic force flows through the wire electron flow through the wire nothing happens electrical force of repulsion flows through the wire. chemicals flow from the battery to the light globe and back to the battery