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37 Cards in this Set

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What properties do all magnets have?
They ALL have:
Two poles
exert forces
are surrounded by a magnetic field
What are the poles of a magnet
The parts of a magnet where the magnetic effects are the strongest. One always wants to point to the north and one always wants to point to the south.
What is magnetic force?
The force of repulsion OR attraction between the poles of magnets.
Describe magnetic force between magnets
Like poles repel each other. Opposite poles attract each other.
What is a magnetic field
The region around a magnet in which magnetic forces can act. The forces radiate in lines from the north to the south pole.
What are magnetic field lines?
They show the way magnetic forces radiate out of a magnet. The closer together the field lines are, the stronger the force is (strongest at the poles)
What makes materials magnetic?
When atoms group together in tiny regions called domains. The atoms in a domain line up and create a magnetic field.
What does it mean when a magnet loses alignment?
If a magnet gets dropped or struck the domains can get jostled out of alignment and it can lose its magnetic properties. Heat can can also cause it to lose alightment.
How do you make a magnet?
You align the domains in the object by rubbing it in one direction with one pole of a magnet. Coming into contact with a magnetic object can align the domains in a regular object and make it magnetic.
What happens if you cut a magnet in half?
You get two complete magnets each with its own north and south pole. That's because each domain within a magnet is like a tiny magnet with its own north and south pole.
What is a ferromagnet?
Magnets made of iron, nickel, cobalt, or an alloy of these metals.
What is the difference between a temporary and permanent magnet?
Temporary magnets are made from materials that are easy to magnetize, but lose magnetism easily, like soft iron. Permanent magnets are hard to magnetize but hold onto their magnetic power better, like alnico (made with aluminum,nickel,cobalt)
Who proved that Earth is a giant magnet?
William Gilbert, an English physician
Explain how a compass works
The needle of a compass always points north because its north pole is attracted to a very large magnetic south pole.
What causes the Earth's magnetic field?
It is produced by the movement of electric charges in the earth's core. The inner core is solid because it is under pressure. The outer core is liquid and as Earth rotates, the liquid flows and causes electric charges to move, creating a magnetic field.
What is an aurora?
A curtain of light that is formed when charged particles from the sun interact with oxygen and nitrogen atoms in Earth's atmosphere and cause the charge particles to emit different colors. It mostly happens closest to the poles because the magnetic field is strongest there.
What is aurora boralis?
The northern lights - an aurora seen near the north magnetic pole.
What is aurora australis?
Auroras seen near the south magnetic pole.
Who discovered the relationship between electricity and magnetism?
Hans Christian Oersted in 1820.
What did Oersted notice when he held a compass near a wire carrying an electric current?
He noticed that the needle no longer pointed north. He figured out that an electric current produces a new magnetic field that depends on the current.
Who did more research on Oersted's theory? What was their work called?
Andre Marie Ampere. Electromagnetism.
What is electromagnetism?
It is the interaction between electricity and magnetism.
What is a solenoid?
A coil of wire that produces a magnetic field when carrying an electric current. If many loops are used to form the coil the magnetic fields combine to produce a much stronger magnetic field. More loops = stronger magnetic field.
What is an electromagnet?
It is a magnet that is made of a solenoid wrapped around an iron core. It can be hundreds of times stronger than just a solenoid.
More Loops
Bigger iron core
More electric current in the wire
ALL equal stronger magnetic field.
Explain how a Maglev train works.
They levitate because there are strong magnets on the cars that are repelled by powerful electromagnets in the rails. They can be turned off or on because they attract only when the current is in the wire.
Explain how electromagnetism makes a doorbell work
When you press the button, an electric current in the solenoid produces a magnetic field. The field pulls the iron rod through the solenoid to strike the bell.
Explain how electromagnetism makes an electric motor work
It has an armature - a loop of wire that can rotate. An electric current in the armature causes a magnet to exert a force which makes the armature rotate. As it rotates, the electric current in the coil changes directions. The current keeps reversing and the armature keeps going around.
How does electromagnetism make a galvanometer work?
A galvanometer is used to measure current. The pointer moves farther when there is a large current in the electromagnet than when there is a small current.
Who proved that you could make an electric current from a magnetic field?
Both Joseph Henry (US) and Michael Faraday (England)
What is electromagnetic induction?
The creation of an electric current by a changing magnetic field (like connecting or disconnecting a battery, or moving a magnet through a coil of wire)
How do we use electromagnetic induction?
To produce electric energy at a power plant, to transmit energy to your home.
Explain how a generator uses electromagnetic induction.
It converts kinetic energy into electical energy. It contains a coil of wire attached to a rod that is free to rotate. It has a crank that is used to turn the coil. The coil is placed between the poles of an electromagnet. Crank turns - coil rotates - magnetic field lines are cut from different directions.
What is alternating current?
When the electric current changes direction continually.
How does a nuclear power plant generate electrical energy?
Heat energy boils water, which produces steam. The steam turns a turbine, which turns the magnet of the generator.
How does a transformer use electromagnetic energy?
It increases or deceases the voltage of an alternating current. It has a ring wrapped with two coils - the primary coil and the secondary coil. They have different amounts of coils, so voltage is either increased or decreased.
Explain how a transformer either "Steps up" or "Steps Down" voltage
If the primary coil around the ring has fewer loops than the secondary coil it STEPS UP the voltage (increases it). If the primary coil has MORE loops than the secondary coil it STEPS DOWN the voltage.
Why does electric current need to be transformed three times before it reaches your home?
The voltage has to be increased to get it to your house, and then decreased (stepped down) before it goes into your local power lines and again before it goes in your house.