Magnetism From Electricity Ch 18.2 8th
description
Transcript of Magnetism From Electricity Ch 18.2 8th
Chapter 18 Section 2
Identify the relationship between an electric current and a magnetic field
Compare solenoids and electromagnets
Describe how electromagnetism is involved in the operation of doorbells, electric motors, and galvanometers
Hans Christian Oersted – discovered the relationship between electricity and magnetism (1820)
Passing a compass under a wire carrying electric current
A compass moves its North-South orientation only when it is in a magnetic field different from Earth’s
Oersted concluded that an electric current produces a magnetic field
The direction of the field depends on the direction of the current
This marked the 1st research about electromagnetism
The magnetic field generated by the current is not very strong
2 devices can strengthen this magnetic field: Solenoid
Electromagnet
Suppose you made many loops in a wire carrying current?
The magnetic fields of the individual loops in a coil combine to make a stronger field (a solenoid)
Similar field as a bar magnet
http://www.societyofrobots.com/images/actuators_solonoid_magnetic_field.gif
A solenoid wrapped around an iron core
Makes the domains inside the iron core line up
100’s of times stronger than just a solenoid
Maglev trains (levitating trains)
http://georgeprice.net/wp-content/uploads/2009/11/electromagnet1.gif
http://www.pause-for-thought.co.uk/www/images/maglev.jpeg
Used in every day life…
Can be used to lift heavy objects containing iron
There are electromagnets in motors
2 solenoids in the doorbell make the doorbell work
Pushing the bell opens the circuit of the 1st solenoid; the current stops causing the magnetic field to drop and the light to go out; the change in the field causes the current in the second solenoid; this current induces a magnetic field that pushes an iron rod that sounds the bell
If a current-carrying wire can cause a magnet to move, can a magnet cause a current-carrying wire to move??
http://www.skoool.co.za/studynotes/science/uploadedImages/Coord12.20_motor_effect.gif
A device that converts electrical energy into mechanical energy
Armature: a loop or coil of wire that can rotate; located between the poles of a permanent magnet
Use direct current
Commutator: attached to the armature; reverses the direction of electric current in a wire
http://ffden-2.phys.uaf.edu/211.fall2000.web.projects/Kristian%20Swearingen/dcmotor.gif
Measures current
Contains an electromagnet placed between the poles of a permanent magnet
The poles of the electromagnet are pushed away by the poles of the permanent magnet
Electromagnet is free to rotate and is attached to a pointer
http://images.hobbytron.com/GI-1309-20-lg.jpg
Explain Oersted’s 1820 discovery
Explain how an electromagnet works