There is a disturbance in the space around a magnet called a magnetic field.

2. Do magnets need to touch a piece of iron or another magnet to exert a magnetic force on the iron or other magnet?

3. There is a disturbance in the space around a magnet called a magnetic field.

4. Magnetic Fields Objects can exert forces on each other through a field even though the objects are not in contact

5. Conduct an investigation to gather evidence that a field exists surrounding a magnet and then create a model that describes a magnet’s magnetic field.

6. An investigative tool The Magnaprobe Note: Avoid touching other magnets with the Magnaprobe’s test magnet. If you do so by accident, hold the Magnaprobe’s test magnet while you pull it off the larger magnet. Do not simply pull back with the handle as parts of the device could be bent or damaged.

7. Tape a magnet in the center of the paper.

8. Place a compass at some location on the paper. Note the direction of the compass needle.

9. Draw a short straight arrow at this location on the paper in the same direction as the compass needle.

10. Or, place the Magnaprobe at some location on the paper. Note the direction the red end of Magnaprobe is pointing.

11. Draw a short straight arrow at this location in that direction. You do not need to make all your measurements on the dots . . . . . . or even in the areas where the dots are.

12. Does this worksheet show evidence that the student conducted an investigation or even made measurements? This is NOT a game of “connect the dots.”

13. Conduct an investigation to gather evidence that a field exists surrounding a magnet and then create a model that describes a magnet’s magnetic field. Verify that your lines are correct by quickly moving the compass or probe all around the magnet again. 

15. A model of a magnet’s magnetic field

17. William Gilbert Conducted investigations on magnetism from about 1581 to 1600 Published results in “De Magnete” in 1600

18. Magnetic Earth • Gilbert observed that when a small compass needle was moved about the surface of a spherical magnet, it faithfully reproduced the behavior of a compass needle on Earth’s surface. • Gilbert's experiments convinced him that Earth itself was a giant magnet.

19. Reminder from last time: HOW TO TELL WHICH IS NORTH AND WHICH SOUTH When a magnet is free to move, the north pole of the magnet will turn around until its north pole is pointing north. HOW ONE LODESTONE ATTRACTS ANOTHER The south pole of one magnet attracts the north pole of another, and the north pole attracts the south. N S N S

20. QUESTION If a magnet will turn around until its north pole is pointing north, what kind of magnetic pole is near Earth’s geographic north pole?

21. Earth’s Magnetic Field

23. Magnetic north pole positions of the Earth. Poles shown are dip poles, defined as positions where the direction of the magnetic field is vertical. Red circles mark magnetic north pole positions as determined by direct observation, blue circles mark positions that have been modelled mathematically.

25. For Salt Lake City, declination is currently decreasing at a rate of about 7 minutes of a degree per year. At the bottom of most USGS topographic quadrangle maps is a diagram that shows three north arrows -- true north, grid north, and magnetic north -- and the angles between them. True north (The star symbol in the diagram indicates true north). Magnetic north (MN) shows the direction a magnetic compass would point at the time the map was published.   Grid north (GN) The difference between true north and grid north is an inherent effect of transforming the earth's spherical surface to a plane surface.