Science Ch. 8

Example of direct current

battery

Step- up transformer

increases voltage, second coil has more turns than 1st coil

Electric current creates

magnetic fields

Where is the magnetic force the greatest in a horseshoe magnet?

near the poles

How can you force an electromagnet to rotate?

with mechanical energy

Generator

Device that produces electric current by rotating a coil of wire in a magnetic field

Two ways a magnet can lose their magnetic behavior

Heating or strike with a hammer

How does a generator work?

1. an electromagnet is placed between the poles of a permanent magnet 2. The coil rotates by mechanical energy 3. Electric current produced as coil turns through magnetic field

How many years ago did greeks discover deposits of a mineral that was a natural magnet?

2000 years ago

Where is the electromagnet on the motor?

Coil

Direct current

Current that flows in only one direction through a wire

Step- down

Decreases voltage, 2nd coil has fewer turns of wire than 1st coil

Galvanometer

Device that uses an electromagnet to measure an electric current

Magnetic field

Exerts a force on magnetic objects represented by field lines.

Turbine

Large wheel that rotates when pushed by steam, wind, or water and that provides mechanical energy to a generator

Where is the permanent magnet on the motor?

Magnet

Three magnetic materials

Nickel, Cobalt, and Iron

Magnetism

Refers to the properties and interactions of magnets

Magnetic pole

Region where a magnet's magnetic force is strongest

Electromagnet

Temporary magnet made by wrapping a wire coil carrying a current around an iron core.

Electromagnetic induction

The process by which moving a wire through a magnetic field produces an electric current

Solenoid

a wire wrapped into a coil

Where is the magnetic field lines the strongest?

at the poles

Where is a voltage source on the motor?

battery

Magnetic domains

groups of atoms in magnetic materials can align their magnetic poles

2 ways to increase the magnetic force?

increase the number of coils or current

Temporary magnets

magnet only when current flowing through a wire.

example of alternating current

outlets

Like magnetic poles always___ each other

repel

The north pole of one magnet will be attracted to the _____ of another magnet

south pole

How is the magnetism lost in a coil?

stopping or starting a current

Alternating current

When a current in a circuit reverses its direction in a regular pattern

Magnetite

a mineral that attracts pieces of iron on it

Explain how a compass works

A compass's needle is attracted to earth's north pole and it always points to earth's magnetic south pole. The needle is a magnet and it attracts to the north pole. The needle of a compass is a freely rotating magnet. The painted end is the south (magnetic) pole of the needle which is attracted by the weak magnetic field of the earth to align itself in a northerly direction (opposite poles attract so the south pole of the compass is attracted to the north pole of the earth's magnetic field). The area to which it points is called the North Magnetic Pole which is close to, but not exactly at geographic North Pole.

Transformer

A device used to increase or decrease the voltage of current in some motors

Electric motor

A machine that changes electrical energy to mechanical energy, used to do work

Permanent Magnet

Magnetize material by placing in a strong magnetic field

What is theorized to cause the earth's magnetic field?

Molten iron and nickel in earths core produce earth's magnetic field