Physics PDF - Magnetism

Magnetism is an important force You may not realise it, but a lot of the things we use every day rely on magnetism—from our computers to our cars! But what is magnetism? How does it work? non-contact force contact force magnetism Newton (N) pole repel magn...

Magnetism is an important force You may not realise it, but a lot of the things we use every day rely on magnetism—from our computers to our cars! But what is magnetism? How does it work? non-contact force contact force magnetism Newton (N) pole repel magnetic materials alloy attract Learning objectives Explain magnetic attraction and repulsion. Apply the concept of poles and the laws of attraction and repulsion. Predict the effects of arrangements of magnetic poles. Force Remember that a force is a push or pull that is applied to one object by another object. Force is measured in newtons (N) The larger a force is, the more newtons it has. Force Forces have both a size (called the magnitude) and a direction. We represent forces with arrows. The direction that the arrow points in represents the direction that the force acts in, and the length of the arrow represents the force's magnitude. Magnetism is a special type of force, called a non-contact force. This means that magnets exert a force on the region around them. A magnet will attract any magnetic materials that are Gravity is another example of a non-contact force. You can still feel close enough. gravity pulling you down to Earth when you jump in the air, and the They do not need to be same principle applies to touching to have an effect magnetism. 3-minute task Select all of the materials that can be attracted by a magnet but do Recall what type of force magnetism is. not generate magnetic forces. Contact force non-contact force Cobalt Platinum Paper Nickel Iron gold Recall which factors are associated with forces. Select all correct options. Direction Color Magnitude Shape Select all of the examples of non-contact forces from the options below. State the unit used to describe forces. Magnetism tension gravity Newtons (N) Joules (J) friction support force Kilogram (Kg) Metres (m) air resistance Think-Pair-Share Think of all the things you use magnetism for in your everyday life.  Magnets Magnets are a special class of objects that generate magnetic forces. This means that they can push or pull on other magnets or magnetic materials. The image shows some very strong neodymium magnets. They are very strong for their small size. Magnetic materials Magnetic materials are special materials that can be attracted by magnetic forces but do not generate their own magnetic forces. For example, the nails in the picture below are attracted to the magnet but are not attracted to each other. This indicates that the nails are made out of a magnetic material! Some common magnetic materials are iron, nickel and cobalt. If you had an iron nail, for example, you could not use it to attract another iron nail, but it would be attracted to a magnet. An alloy is a metal that is made of a combination of metals. Alloys made of iron, nickel or cobalt are also affected by magnets. Steel is an example of an alloy that is attracted to magnets. There are special processes that turn magnetic materials into magnets. This is called magnetisation.  All magnets have a south pole and a north pole. The south pole has the symbol S and the north pole has the symbol N One common type of magnet is the bar magnet (pictured below).  A bar magnet is a type of permanent Permanent Magnet magnet, which means that it always produces a magnetic force. When two bar magnets are brought together, they will either attract or repel each other. When two like poles are brought together, the magnets will repel each other. When two opposite poles are brought together, the magnets will attract each other. Describe what an alloy is. A material made from the combination of metals A material that can never be attracted by a magnet A material that generates a magnetic force Define the term magnet A material that never generates a magnetic force A material made from the combination of metals A material that always generates magnetic force Identify if these magnets will attract or repel each other. Summary Magnets are objects that generate magnetic __________. Magnetic ___________ are objects that respond to magnetic forces but do not generate magnetic forces. Every magnet has a south pole and a _________ pole. When like poles of two magnets are held together, the magnets will ___________ each other. If opposite poles are held together, the magnets will___________ each other. Analysing magnets and magnetic materials. Compare magnets and magnetic materials.  Homework 1. Describe the rules about magnets attracting and repelling each other. 2. Describe what will happen in each of these situations: a. The N pole of a magnet is brought towards the S pole of another magnet. b. The S pole of a magnet is brought towards a piece of magnetised iron. c. The N pole of a magnet is brought towards a piece of copper. 3. Explain why a magnet hanging on a thread will respond to magnetic forces more easily than a magnet laying on a bench. Explain, using examples including magnetism, the differences between contact and non-contact forces. Someone states that ‘magnets stick together’. What would be a better explanation of the behaviour of magnets? Explain the similarities and differences between the Earth’s gravitational and magnetic forces.