Ch. 3; Lesson 3.2

T.O.C:Current Can Produce Magnetism

Electric Current Produces a Magnetic Field• 1800’s- Hans Christian Oersted discovers a

connection between electric current & magnetism :• Electric current produces a magnetic field which can

cause objects to become magnetized

• Electromagnetism w.w- magnetism that results from an electric current.• When a charged particle –electron- moves; it produces

a magnetic field.• If wire is straight- magnetic field is like a tube around

wire, if wire is loop- magnetic field is stronger & is concentrated inside the loop. The more coil, the more concentration → stronger magnetic field

• Coiled wire w/ charge flowing has magnetic field like a bar magnet.

Create coil/wire/bar magnet illustration

Making an Electromagnet• Electomagnet -w.w. – magnet made by placing

a piece of iron or steel inside a coil of wire. • As long as the coil carries a current, the metal

will act like a magnet & increase the magnetic field of the coil.

• When current is turned off, magnetic domain in the metal becomes random again & magnetic field/properties are gone.

• The more coils of wire around metal → stronger electromagnet

• Some of the most powerful magnets in the world are hug electromagnets used in scientific experiments.

Uses of Electromagnets• B/c they can be turned on/off, they have more uses than

permanent magnets. • Ex:

• Crane in junkyard w/ huge magnet or like the one in the background image move extremely large objects..

• Computers use electromagnets to store info• ATM/Debit/Credit cards have information in strip swiped at

store/bank – don’t store cards w/ strips facing each other b/c the magnetic field can cause info to erase

LAB-Build an ElectromagnetLabs/Activities section of Notebook- Leave space between each ↓

List materials needed, -wire, iron nail, battery, paper clip How you built your magnet. –build without a switch 1st Make a switch for you electromagnet. Change the amount of coils in your wire- what was your electromagnet with less coils like? With more coils?

Change battery sizes- does the size of the battery affect the power of your electromagnet positively, negatively, or not at all?

Motors use Electromagnets• Electric motors convert the energy of an electric current into motion

by using current & magnetism• 100’s of devices contain electric motors: blender, mixer, fans, power

tools. – Almost anything with moving parts that uses current has an electric motor.

About Motors• Although they may look different in size/appearance, all motors have

similar parts & work in similar ways.• Main parts of an electric motor:

– Voltage source, a shaft, and electromagnet, & at least 1 additional magnet. The shaft of the motor turns the other parts of the device.

• When current from the voltage source flows through the coil, a magnetic field is produced around the electromagnet. The poles of the magnet interact with the poles of the electro magnet, causing the motor to turn.– The poles of magnet/electromagnet constantly exert force pushing/pulling

each other causing the motor to turn. – When the poles line up with their opposites, part of the motor – commutator -

reverses the polarity of the electromagnet & the motor keeps turning.– The more coils on the electromagnet in the motor, the stronger the motor

Uses of Motors• Motors can move very small objects- like

battery operated hands on a wrist watch; or very big, such as the motors that power subway trains.

• Motors can move objects in any direction. Ex: some motors move objects in circles- CD player, gaming device- & some move objects up/down- power window motors in cars move the windows up/down

• You can have more than 1 motor in the same device.

LAB- Build an Electric Motor

3.2 Review Q’s (12 pts

1. Explain how electric current & magnetism are related. (2 pts

2. Describe 3 uses of electromagnets. (3 pts3. Explain how electric energy is converted

into motion in a motor. (3 pts4. How does an electromagnet differ from a

permanent magnet? (2 pts5. What 2 ways can you increase the

strength of an electromagnet? (2 pts)