Electricity and Magnetism

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Farragut Intermediate School PTA

Atoms and Electric Charge

• Everything is made of atoms
• Atoms are made of particles

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Atoms and Electric Charge

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• Atoms can gain or lose electrons

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Electric Charge

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• Similar charges REPEL
• Opposite charges ATTRACT

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Magnetism

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• Electrons can “point” the same way

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Nonmagnetic:

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Magnetic:

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Two Types of Magnet

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• Permanent
• Magnetic poles are “frozen” in place

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• Electromagnet
• Made by running current through coiled wire

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• Can be turned on and off

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Magnetism

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• Magnets produce fields that attract or repel other objects.

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• Two poles: (north and south)

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• Field is strongest at the poles.

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Earth’s Magnetic Field

• Protects us from radiation
• Lines of force run North – South
• Can find using a compass

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Magnetism

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ACTIVITY:

Floating magnets

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Electricity

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• Electricity = energy from electrons

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• Static = buildup of charge

• Current = moving charge

Static Electricity

• Rubbing things together makes them electrified

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• Electrons move from one surface to the other

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• Surfaces develop opposite charges:

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• Gain electrons = (-) charge
• Lose electrons = (+) charge

Static Electricity

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• Electric charges separate & build up

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Opposite charges attract

Similar charges repel

Static Discharge

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Static Electricity

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ACTIVITY:

Static tubes

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Static tubes are fragile. DON’T BREAK THEM!

Static Electricity

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Why do the balls

stick to the sides?

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Why do the balls

“jump” away from

your finger?

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Opposite charges attract

Similar charges repel

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Electric Current

• Electricity can flow in a current

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• Current must:
• Follow a complete path (a circuit)
• Have a power source:

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Circuits

• Circuits can be open or closed
• Current can only move in a closed circuit

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• Control current with electrical components like switches or resistors

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Insulators and Conductors

• Conductor – a material through which electricity flows easily

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• Insulator – a material through which electricity does not flow easily

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Increasing Conduction Ability

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Insulators Semi-conductors Conductors

Pure Glass Rubber Wood Diamond Silicon Water Iron Aluminum Copper Silver

Water

Activities

Conductors & Insulators

Simple Circuit

Series Circuit

Motors

Electromagnets

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Be gentle. Equipment is breakable!

Magnetism – Discussion

• Where is the magnetic field strongest on a magnet?

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• Name two kinds of magnets.

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• What happens if you break the electromagnet’s circuit?

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• Why do all compass needles point the same way?

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Electricity - Discussion

• Name the particle that flows through wires in a circuit.
• Would a (-) charge attract a (-) or (+) charge?
• Will a light bulb work when the circuit is open?
• Does electricity flow better through a conductor or an insulator?
• What happens when you flip on a light switch? Is the circuit open or closed?