Magnets & Magnetism

The discovery of magnets In Magnesia in Ancient Greece, there lived a shepherd named Magnus One day, he was looking after his sheep in the hills.

The discovery of magnets All of a sudden, he felt a mysterious force pulling his iron staff from his hand. Even the iron nails on his sandals were being pulled out.

The discovery of magnets To his great surprise, he discovered that it was a huge, black rock next to him that was pulling his staff and the nails.

The discovery of magnets Soon, news spread across the country about the strange rock (now called lodestone) that had the power to pull things to it.

The discovery of magnets The Greeks later found other similar black rocks which had this power. These rocks were named ‘magnets’, after either Magnesia or Magnus himself.

Magnets Today Magnets are one of the most important forces in our world There is a magnet or an electromagnet inside many things

Magnets Today Computers store data in magnetic disks and CDs. Electromagnets are used to lift heavy objects

Magnets Today Maglev trains ‘float’ on top of tracks Doctors can see the inside of our bodies thanks to magnetic resonance imaging (MRI)

Magnets Today The Earth has a magnetic field which we can use for navigation

What is magnetism? Magnetism: an invisible force that pushes or pulls magnetic material. Which materials are magnetic?

Magnetic Materials Materials that are ATTRACTED TO A MAGNET, but do not attract or repel each other. steel spoon and knife iron nails

Are all metals magnetic? cobalt (Co) gold (Au) iron (Fe) nickel (Ni) copper (Cu) zinc (Zn) magnesium (Mg) aluminium (Al) silver (Ag)

If you said NO you are CORRECT cobalt (Co) nickel (Ni) Only iron (Fe), nickel (Ni) and cobalt (Co) are magnetic. iron (Fe) zinc (Zn) magnesium (Mg) gold (Au) aluminium (Al) silver (Ag) copper (Cu)

Non-magnetic Materials Materials that are not attracted to a magnet. …metals such as gold, aluminium, silver and copper. copper container Aluminium jewelry gold jewelry

Non-magnetic Materials Non-metals such as plastic, wood, paper, glass and clay are non- magnetic materials.

Magnetic induction When a magnetic material is close to a magnet, it becomes a magnet itself. We say it has induced magnetism. magnet N S S N

Soft Magnetism Pure iron is a soft magnetic material It is easy to magnetize but loses its magnetism easily before after N S S N N S N Not a magnet Iron nail

Hard Magnetism Steel is a hard magnetic material It is harder to magnetize, but keeps its magnetism (it is used to make magnets!) before after S N S N N S S N N It’s a magnet! Steel paper clip

Sum this up You have 5 minutes to sum up induced magnetism, soft magnetism and hard magnetism. Use the key words below to help you. Induced magnetism, north pole, south pole, magnet, pure iron, magnetize, steel, permanent magnet, soft & hard magnetism.

What else should we know about magnets?

A magnet has 2 poles bar magnet Poles – part of the magnet with strongest magnetic force. The poles are called North pole and South pole bar magnet

If you bring 2 bar magnets close together… Two Opposite poles attract Law of Magnets If you bring 2 bar magnets close together… Two Opposite poles attract

If you bring 2 bar magnets close together… Two Like poles Repel Law of Magnets If you bring 2 bar magnets close together… Two Like poles Repel

If you cut a magnet in half, you get… 2 smaller magnets, each with 2 poles. If you cut a magnet into many pieces, each piece is a magnet with 2 poles.

Taking a closer look: Materials are made of many tiny electrons. They are always spinning around. Domain - A group of spinning electrons. Each domain acts as a tiny magnet. In non-magnetic materials, the domains are pointing in all directions.

Domains inside magnetic materials In magnetic materials, the domains are pointing in one direction. The domains (tiny magnets) are working together and make the entire object magnetic.

Domains inside magnetic materials In magnetic materials, the domains are pointing in one direction.

Domains inside magnetic materials Domains aligned Magnetic Domains random Not magnetic

Magnets create magnetic fields A magnetic field is the area around a magnet where there is a magnetic force Magnetic force is invisible, so how can we draw the magnetic field lines?

Magnets create magnetic fields If you put some iron filings around a magnet, you can see the magnetic field lines. strongest field at poles weakest field further away from poles

Magnets create magnetic fields The direction of the magnetic force is from NORTH to SOUTH

Magnets create magnetic fields Two like poles repel

Magnets create magnetic fields Two opposite poles attract

The earth has a magnetic field Earth’s core has molten iron and nickel which is always spinning The spinning core acts like a magnet

Magnetic north pole and geographic north pole are not at the same place.

How to plot a magnetic field You will need to follow these instructions very carefully! 1. Put a blank piece of paper on the table in a landscape layout.

How to plot a magnetic field You will need to follow these instructions very carefully! 2. Put the title of Plotting a Magnetic Field, the Date, and your name on your paper. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 3. Place a bar magnet in the middle of the page and draw around it. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 4. Take the magnet off and divide the rectangle in half. Colour each end. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 5. Take a plotting compass and place it in the position shown below. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 6. Using a pencil, put a dot on the paper where the needle is pointing. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 7. Now place the CENTRE of the plotting compass over the dot you just made. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 8. Now put another dot where the needle is now pointing. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 9. Place the plotting compass over the new dot and repeat this process. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 10. Keep going until you either go off the page or you loop back around to the other side of the magnet. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 11. Now place the plotting compass in a new starting position. Try and ‘mirror’ the line you have just done. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 12. Keep repeating this process completing as many lines as possible within the lesson. Try lots of different starting points. 16th Sept. 2016 Ms Holland Plotting a magnetic field

How to plot a magnetic field You will need to follow these instructions very carefully! 13. If you are successful, you should end up with a pattern like the one below. 16th Sept. 2016 Ms Holland Plotting a magnetic field The more lines you do, the better the diagram.