1. Electromagnetism

2. Imagine a world without
Talking on a telephone
Watching TV
Listening to a radio or CD
Not being able to use anything that plugs into a socket

3. Hans Christian Oersted
In 1820 he was doing a demonstration using electric current.
As he passed current through a wire, a compass needle deflected.
He discovered that magnetism is related to electricity.

4. Electricity and Magnetism
Charge at rest  electric field
Charge in motion  magnetic field

5. Electromagnetism Lab

6. Right hand rule # 1
If straight wire is grasped with the right hand, with the thumb pointing in the direction of current, fingers will purl in direction of magnetic field.

7. Vertical Conductors X
Out of the page Into the page

8. Solenoid
Linear coil of conducting wire

9. Right hand rule #2
When a solenoid is grasped with the right hand, so that the finger curl in the direction of the current, the outstretched thumb will point toward the north pole of the magnetic field.

10. Electromagnet
Solenoid with a soft iron core

11. Demo How can you make an electromagnet stronger?
How is an electromagnet different than a permanent magnet?

12. Relationship Between Electricity & Magnetism
Electricity can create magnetism
Moving charges create a magnetic field around the wire carrying that current
Can a magnetic field be used to make charges move?

13. Michael Faraday and Joseph Henry
In 1822,faraday wrote a goal in his notebook: “Convert magnetism into electricity”
10 years later, he and Joseph Henry, another smart high school teacher, independently made the big discovery that changed the world.
They discovered Electromagnetic Induction

14. Electromagnetic Induction
Process of generating a current in a circuit by changing a magnetic field.
Magnetic field lines must be cut perpendicular by relative motion of magnet and conductor.
Either the magnet can move or the wire can move.

15. Factors affecting magnitude of Induced Current
Amount of conductor or coils of wire
Strength of the magnetic field
Speed of motion

16. Right Hand Rule 3
When the fingers point in the direction of the magnetic field, (toward the south pole of the magnet) and the thumb points in the direction of the motion of the wire, the palm pushes in the direction of the induced current.

17. Electric generator Invented by Faraday
Converts mechanical energy to electricity
Wire loop (armature) rotates in a strong magnetic field to induce a current

18. What happens when current flows through a wire?
Demo: Lenz’s Law

19. Lenz’s Law Induced current opposes the motion that induces it
Work must be done to overcome the magnetic repulsion

20. Electric Motor Has same parts as generator
Converts electric energy to mechanical energy
Current moves through the armature inside a magnetic field, making armature turn.

21. Demo Simple Motor

22. Generators and Motors Phone has both generator and motor
Mouthpiece has generator to convert motion of voice into electrical impulse
Earpiece has motor to convert electrical energy into mechanical motion of the speaker.
Both contain magnets and electromagnetic devices.