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EXPLORING MAGNETISM What is a Magnet? What Materials are Magnetic? What Materials are Magnetic? What Do Magnets Do? Attract or repel other magnets (exert a force) Attract other magnetic metals Have 2 distinct ends (poles) – N and S Like poles repel, opposite poles attract Notes: Magnets do not need to touch to exert force (can exert force through empty space) They can turn other magnetic metal objects into temporary magnets Magnetism in a Magnet When elements like Fe form solids, they form crystalline structures with little domains of many, many atoms all aligned in the same direction. Each domain is like a mini magnet. When all the domains are allowed to align, the whole object takes on a large-scale magnetic field. Magnetic Field Lines Magnetic field of a bar magnet: 2 poles, called North and South Dipole field Field has direction: lines point away from N and toward S Definition of a Pole: Where lines meet (converge) e.g.: lines of longitude on a globe meet at poles Earth: A Huge Bar Magnet Magnet Moving molten iron in Earth’s outer core causes most of Earth’s magnetic field. Magnetic field poles are NOT aligned with geographic poles. They also wander and flip (500,000 yrs between flips, 10,000 yrs to complete flip). Activities: Investigating magnetism Collect for your group: 2 bar magnets, a nail, some paperclips, iron filings, an OHP transparency sheet. What to do: 1. Try using a magnet to pick up some paper clips and also try holding it near some iron filings. 2. Find out what happens when you put 2 N poles, 2 S poles and a N and S pole of the two magnets together. 3. Place a magnet under the OHP sheet and scatter iron filings over it. Draw what you observe on p86 of your Sci Pad. 4. Repeat Activity 3 using both magnets arranged as in Activity 2 (but without the magnets actually touching). Draw on p87. 5. Try to magnetise the nail by stroking it several times in one direction with one of the magnets. Can you pick up paper clips with the nail? Drop the nail on the floor then try it again. ELECTRICITY MAGNETISM Electric currents cause magnetism • How can you tell? Compass needle moves when near electrical current creating an magnetic field ELECTROMAGNET A magnet with a field produced by an electric current Electromagnetism a moving charge (electricity) produces a magnetic field • More coils of wire= more current = stronger magnet • Bigger battery = stronger magnet Making an electromagnet Collect for your group: a battery, some copper wire, a nail and some paperclips. What to do: 1. Wind the copper wire tightly around the length of the nail leaving about 10 cm of wire free on each end. 2. Hold the wire wrapped nail near the paperclips and see if it will pick them up. 3. Attach the free ends of the wire to the battery terminals. 4. Repeat step 2 with the wire wrapped nail attached to the battery and note what happens. 5. How could an electromagnet be useful? MAGNETISM ELECTRICITY A moving magnet can generate electricity • How can you tell? Electromagnetic induction moving a magnet in and out of a coiled wire creates an electrical current without using a battery. This principle is used to generate electricity. Water, wind or steam are used to move huge magnets which produces an electric current. Generating Electricity • https://www.youtube.com/watch?v=20Vb6 hlLQSg (Energy production) • https://www.youtube.com/watch?v=d_aTC 0iKO68 (Electric motors and generators) • https://www.youtube.com/watch?v=AmWE s5CTQ3Q (How is electricity produced?) • https://www.youtube.com/watch?v=E8QF8 uRCEtE (How is electricity produced?) • https://www.youtube.com/watch?v=NsQiVI Py6CA (Electricity production – for kids)