ELECTROMAGNETISM
The marriage of electricity and magnetism
ELECTROMAGNETISM
Different aspects of the same force:
Electromagnetic Force
Four fundamental forces of nature
Gravity
Nuclear
Nuclear Interaction
Electromagnetism
HISTORY
Luigi Galvani = Frog leg
Alessandro Volta = Voltaic pile (Battery sandwich)
Stacked copper and zinc together with a layer of wet paper between metals producing a weak current
Invention of the battery led to the understanding of electromagnetism and their symbiotic relationship
Modern batteries
Positive carbon rod
Surrounded by electrolytic paste
Housed in a negative zinc.
Invention of the battery led to the understanding of electromagnetism and their symbiotic relationship
Therefore a battery is a source of conversion of some form of energy (magnetic) into electric current
Battery is a source of EMF
Hans Oersted
Discovered the relationship between magnetism and electric current
A magnetic field is produced by current running through the wire
"Hand" Rules
Right Hand rule
Thumb indicates the direction of the current
Fingers indicate direction of magnetic field lines
Fleming’s Right Hand Rule
Determines the pole of the solenoid
Thumb points to the north pole, Fingers represent the direction of the current
Flemings right hand generator rule:
Thumb is the direction that the conductor is moving
Index point to the direction of magnetic lines
Middle finger=current flow
"Hand" Generator rules
Flemings left hand generator rule:
Thumb is the direction that the conductor is moving
Index point to the direction of magnetic lines
Middle finger=electron flow
Faraday Rule
AKA: 1st law of Electromagnetism
A magnetic field cannot be still and produce a current. But if the magnet is moving a current is produced.
Furthermore: Induced current by a magnet depends on
Strength of magnetic field
Velocity of magnetic field
Angle of the conductor to the Magnetic field
# of turns in a conductor
Answers: 99-B
100 - C
TO PRODUCE electric current
Move a bar near a coil of wire
OR
Move coil of wire near stationary magnet
Current increases with increase in magnetic field
LENZ’S LAW
Most important thing to remember even if you do not understand this law is the following:
It is the basis for self induction
The autotransformer and choke coil in an x-ray circuit both run on self induction
HERE WE GO
Lenz’s Law: Induced current flows in a direction such that it opposes the action that induces it
Lenz’s Law answers this question
Which end of the coil that has had current induced will be the north or south pole?