Electromagnetism and Motion

Page 85

Students will be able toDescribe a galvanometerExplain electric motorsExplain how generators workContrast AC/DC currentsDescribe how a transformers work

Electrical Energy

Occurs when you have motion between magnets

86

Galvanometers

87

Take advantage of motion to measure small currents

Motors

Three key partsArmature – Loop just like in galvanometer

Rotates in magnetic fieldBrushes – Carry charge from source

Do not moveCommutator – Carries current to armature

Attached to armature and moves.

88

Motors

88

Induction

When a wire moves through a magnetic field

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Induction

95

Or move a magnet through wires

Direct Current

DCThe electric current flows in one direction only

Batteries

96

Alternating Current

ACCurrent repeatedly changes directionUsed in homes, school…Allows for easier control

Easily raised or loweredHigh for shippingLower for home

97

Generators

The opposite of an electric motor

98

Generators

Turbines

99

Transformer

A device that can increase or decrease voltage

99

Types

Step-up vs Step-down

100

Devices

Big equipment – Step up voltageFluorescent lights, TV

Small stuff – Step downElectronic games, ipod, CD player… (12V)

101

Question of Day

You are a television reporter covering the opening of a new dam that generates electricity. Write a short news story describing how a dam transforms mechanical energy from the motion of the water into electrical energy.