ELECTROMAGNETISM

Unit 8: Electricity and Magnetism

Magnets

• The ends of a bar magnet are called poles
• Like poles repel and unlike poles attract
• Regardless of their shape, all magnets have a north and south pole

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Magnetic Fields

• Magnetic field lines point from the north pole to the south pole of the magnet
• The north pole of a compass needle always points in the direction of the field (from North to South)

Earth’s Magnetic Field

• The Earth’s geographic North pole is actually the magnetic South pole
• A compass points towards geographic north and since opposites attract, we know that the Earth’s geographic pole is magnetic south

Magnetic Field of a Wire

• Moving charges produce magnetic fields
• If there is a current moving through a wire, a magnetic field is produced around the wire

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Magnetic Field of a Wire

• The Right Hand Rule
• Point your thumb in the direction of the current (I) and your fingers curl in the direction of the field (B)

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Electromagnets

• An electromagnet is a type of magnet in which the magnetic field is produced by electric current
• A metal core cylinder is inserted in a solenoid
• A solenoid is a coil of wire carrying an electric current

solenoid

core

wire

battery

Electromagnet Strength

• The strength of an electromagnet is affected by:
1. The core material
2. The current intensity
3. The number of loops

1. Core Material

• A core is the object inserted into the solenoid, creating an electromagnet
• Ferromagnetic cores strengthen the magnetic field
• Ferromagnetic: materials that become magnetized easily: iron, steel, nickel, and cobalt
• Wood, plastic, and aluminum are poor materials for a core

2. Current Intensity

• More amps = more strength

STRONGER

3. Number of Loops

• More loops = more strength

STRONGER

8.5 LESSON CHECK