MAGNETISM
Magnetism is one of the strangest things in nature! What happens is a dance of electrons!
It’s believed a shepherd discovered the first magnet when a rock stuck to a nail in his sandals! A wall of magnetic stones pulled a W. Va. miners helmet off his head! Magnetite or lodestones are natural magnetic rocks found in iron deposits and they get there because a bacteria that breathes without oxygen, enjoys the dark and likes to eat iron. When they digest iron it is turned to magnetite. Many animals have cells that contain magnetite. Scientist think magnetic cells help animals (bees, tuna, dolphin and whales) find food and migrate. In certain parts of their brain we find magnetite. It may help them tell up from down. Whales have been stranded in areas of irregular magnetic fields. Humans have a small amount of magnetite lining their noses. Scientists think our noses were once like compasses!
Magnets attract certain objects and produce magnetic fields which come together at the poles. Opposite poles attract. The magnetic force is strongest at the poles and weakest at the center. The magnetic field is the lines of force around an object. Like poles repel / unlike poles attract.
Pure metals have the same kind of electrons. Atoms are the basic substances of the universe and the nucleus and electrons have opposite charges. Different substances have a different # of electrons circling around the nucleus. Electrons form a sort of cloud around the nucleus. Atomic particles may spin, charge in motion, and have a magnetic moment. The spinning motion makes the larger atom magnetic. Electrons may spin in the same or opposite directions. If 2 spin the same it is a strong magnet. If 2 spin in opposite directions they cancel each other and have a magnetic moment of 0. Atoms of certain elements line up in domains and have a magnetic field.
Ferromagnetic – magnets such as iron, nickel, cobalt lodestone (the magnetic atoms of the same substance turn toward and away from a magnet because of a peculiar crystalline structure.) Ground up magnetite is mixed with plastics to make refrigerator magnets. Powdered ferrites coat magnetic recording tapes.
Paramagnetic means having a slight magnetism such as gold, copper, aluminum and can be detected with a magnetometer. If you make an aluminum pan cold enough it will behave like an iron magnet.
Diamagnetic includes silver and most others and is the natural magnetic quality of all matter – even human tissue. Human tissue responds to a strong magnetic field. Stand next to a strong magnet, the atoms in your body repel the magnet!
Temperature and magnets – If the temperature of ferromagnetic metal is raised, the magnetism disappears. The point that it loses its magnetism is called the Curie temp. If you lower the temp of rare earth metals, they become magnetic. Atoms of materials shift around in different ways. Magnetite (3 iron, 4 oxygen) is found in any good rocky area and resembles grey lumps of coal heavy for their size. Use a compass to find them.
Blood hemoglobin contains iron that gives blood its red color. Hematite (rust) is a more common compound of iron. Lodestone has large crystals of magnetite and a permanent magnetism. A Chinese compass uses lodestone floated in water on a small boat. The density of magnetite is over 5. 1 cup of magnetite weighs 5 times that of a cup of water. Pure iron has a density of 8.
If you freely suspend a bar magnet it lines up like a compass and always has a north and south pole. Magnetic particles line up in the same direction. Dropping or heating a magnet will damage it and cause the particles to shift positions. Magnetic transparency is the ability of a magnet to attract through non-magnetic materials. Most materials are non-magnetic. Metals attracted to a magnet are called FERROMAGNETIC like iron. Iron has the strongest attraction to a magnet. Copper, aluminum and gold have weak attractions. Magnets can be created. In 1820 Oersted discovered that electricity produces magnetism. Wherever electricity goes, magnetism follows = electromagnetism. A dry cell battery coil of wire around nail makes a temporary electromagnet. Electromagnetic waves travel through anything, even through a vacuum. Magnets are used on cranes, latches, stud finders, doors, tapes, VCRS, TVS, bells, buzzers, machines ,vacuums, speedometers, computers, credit cards, automatic tellers and in physical therapy.
MATERIALS: Magnetic wands, small amt. of Total cereal, paper clips, 3 nails, materials for magnetic sculpture, 2 bar magnets, round magnet, horseshoe magnet, compass, balloon, salt, pepper shaker of iron filings, 3 feet of insulated copper wire, 6 volt battery, liquid crystals, rust mixed with sand.
ACTIVITIES:
- Have a ferromagnetic scavenger hunt!
- Test magnets through different materials.
- Do magnets work through water?
- Create a magnet sculpture.
- See how many paper clips you can hang from each other.
- Cereal contains iron (Total works best) and you can pick up particles with a magnet.
- A magnet erases tape recordings.
- The needle of a compass is a magnet.
- A compass on the North Pole will spin in circles.
- The forces of attraction and repulsion may be strong or weak.
- Any moving magnetic field will produce an electrical current.
- Rub a balloon on hair 12 times and you can pick up salt.
- Horseshoe magnets work well lifting heavy objects. Because the poles are close together, they combine strengths.
- Magnetic field examples: Put filings in a pepper shaker and test fields by putting beneath paper a bar magnet, a round magnet and a horseshoe magnet.
Bipolarity is one of the most puzzling differences between magnetism and electricity. Magnetic fields have 2 poles that cannot exist apart. If you break a magnet apart, a North and South Pole appear at the ends of the 2 pieces (like the brooms in the sorcerer’s apprentice!) The magnetic field always wraps around itself, flows into itself, and can never separate from its poles. Electricity can only travel in one direction. There is an odd relationship between electricity and magnetism. A magnetic field produces electricity. An electric current creates a magnetic field. Magnetism passes through many materials that do not conduct electricity ex. glass, plastic. When electricity passes through a wire it creates a magnetic field around the wire and you can reverse the current and reverse the poles.
An MRI is magnetic resonance imaging. The machine is like a big donut and takes a picture by reading the turning of atoms in tissue.
Dating with magnets = Thermo remnant magnetic dating notes the direction of the poles of magnets found in the ground.
Bombs in WWII: Nazis dropped mines on bottom of rivers with inclinometers and when a ship passed over, it triggered them. The ships had to be demagnetized.
Liquid crystals change when exposed to magnetic fields and can shut out light like closing a shutter. They are large irregular molecules such as nitrobenzene
Plasma magnetism in the future? = magnetized water. Lightening changes water so more nitrogen sticks to it. To gather micrometeorites in water the best time is Aug. 11 – Dec. 13
Earth is the biggest magnet. We think it is from the huge electric currents deep within where molten iron surrounds a solid core of iron. The motion creates electricity. The earth’s magnetic field can change. It is believed the poles reversed at one time. In ancient clay banks magnetite needles are frozen in time and N points south. If you are close to one of the poles the needle stands on end. An inclinometer measures the angle of dip to figure out distance from pole. A magnet can cause damage to computers and tapes.
Insulators are shields to protect against magnetism.
Experiments:
1. Make a nail into a magnet: Dissolve the domains and make them line up in the same direction. You will need 3 nails of iron. Stroke a nail with a bar magnet 20 times and touch the staples to test. Pound a nail with hammer holding with end pointed north. It will break apart the domains and force atoms to line up. Wrap 3 foot insulated copper wire around a nail and connect the ends to a 6 volt battery – electric current flows in one direction ( electromagnet) is used on cranes to pick up scrap metal. You can switch it on and off. If you remove copper wire staples drop and it loses magnetism
2. Experiment: Observe the Poles. Use 2 bar magnets and dip N pole of one in filings. Dip S pole of other in filings. Notice how filings hang on when put together or pull apart. Dip both N poles in filings. Put together and pull apart. Filings will repel each other
3. You need a ruler, bar magnet and staples. Slide magnet toward staples and measure when pulled. Try through plastic, cloth, tissue, foil, rubber, glass slide. None work well as insulators, a strong magnetic field goes through everything
4. Attach ball bearings to end of bar magnet. 3rd ones push apart. Add the 4th and join. Both attract and create 2 north poles in 7th bearings
5. Mix rust and sand put in saucer and push around to pick up with magnet.
6. There are 2 kinds of compass = radial and dip. Magnetic suspension cushions objects. Mr.Farraday discovered the magnetic dynamo with a copper wire wrapped into circle and tied with 4 twist ties. Wrap free ends of wires around compass in same direction connecting the wires. Move bar magnet in and out of center and the compass needle jumps. The movement produces an alternating current.
7. Heard of levitating ladies with bar magnets! Magnetism is stronger than the force of gravity. Make a magnetic wand for tricks.
Game: Go fish with magnets. Punch holes in fish for points. If catch tire then put fish back or lose turn
Get magnetic wands here: Magnetic Wands