1. The Physics of Electricity and Magnetism Making a Magnet 9-12 Science Std: Phys 5h, 5j

2. First, a quick review about magnets Magnets are usually metals or ceramic They come in many shapes Horseshoe magnets Flat magnets that can go on a refrigerator Bar magnets NS

3. First, a quick review about magnets But these magnets all have some things in common… They all attract things that contain iron Nails, paper clips, etc They are most strongly attracted to the ends of the magnets – called the poles of the magnet There are 2 poles – called the North Pole and the South Pole Opposite poles attract, same poles repel Lines of force (magnetic field) surround the magnet going from north to south

4. First, a quick review about magnets And you have heard of electromagnets….. Wrap some wire around a nail and put current through it… And you get a magnet just like a bar magnet with a north and a south pole… But how does a bunch of electrons moving through a wire make a magnetic field? NS

5. How does this work? Scientists in the late 1700’s started working on this… They thought that electricity and magnetism worked together somehow But no one had an idea how they worked together So they didn’t know where to start….

6. How does this work? Then in 1820, an experiment was done….. Hans Oersted did an experiment with a wire and a compass He held a wire next to a compass and ran a current through it

7. How does this work? Then in 1820, an experiment was done….. When the current was turned on…. The needle of the compass turned away from pointing towards North

8. How does this work? Then in 1820, an experiment was done….. When the current was turned off The needle went back to pointing to North Disc 19 Demo 8

9. How does this work? Why did the compass needle move? When an electrical current flows through a wire A Magnetic field is created by the moving electrons that wraps around the wire

10. How does this work? Why did the compass needle move? Here is a video demonstration showing the magnetic field around a wire….. Disc 19 Demo 9

11. Lets look at the magnetic field…. Which way does the magnetic field go? From the video we saw that the iron filings made a circle around the wire

12. Lets look at the magnetic field…. Which way does the magnetic field go? We also saw how the iron filings take shape around a coil of wire…

13. Lets look at the magnetic field…. But why does the magnetic field have these shapes? When the current goes through the wire A circular magnetic field wraps around the wire using the Right Hand Rule

14. Lets look at the magnetic field…. What is the Right Hand Rule? Imagine your pencil is a wire carrying an electrical current Now picture the current going from the bottom of the pencil to the top….

15. Lets look at the magnetic field…. What is the Right Hand Rule? Now take your right hand And wrap it around the pencil with your thumb pointing in the direction the current is going

16. Lets look at the magnetic field…. What is the Right Hand Rule? Your fingers are wrapped in the direction of the magnetic field

17. Lets look at the magnetic field…. What is the Right Hand Rule? We can see this better in the video demonstration using a wire and a compass…. Disc 19 Demo 7

18. So now lets try it ourselves….. Using the Right Hand Rule… If we have a wire like the one here… And the current is flowing from top to bottom…. Which way is the magnetic field going to go?

19. So now lets try it ourselves….. How about this one…. If we have a coil of wire….. And the current is flowing from top to bottom…. Which way is the magnetic field going to go? Disc 19 Demo 10 So this will look just like a bar magnet!

20. Important things to remember… Electrical current makes a magnetic field The more the current, the stronger the magnetic field The direction of the magnetic field is shown using the Right Hand Rule NS

21. Important things to remember… Current through a coil of wire makes an electromagnet Electromagnets are just like regular magnets They have north and south poles NS