Electromagnetism (RADS 354)

Electromagnetism

branch of physics that deals with the relationship between electricity and magnetism

more current

more lines of flux

if current decreases, what happens to flux?

it decreases

How do we determine the direction of magnetic flux?

Left Hand Thumb Rule

left hand thumb rule

grasp the wire with your left hand, the thumb is the direction of current, and the finger is the direction of the lines of flux

Helix

a wire fashioned into a coil

Solenoid

a helix carrying an electrical current

Electromagnet

A solenoid with an iron core inserted into the coil of wire

Can a magnetic field generate an electrical current? Faraday discovered:

that by rapidly passing a wire between the poles of a horseshoe magnet, an electrical current is produced in the wire

Electromagnetic Induction

whenever a conductor cuts across magnetic lines of flux, or whenever a conductor is cut by magnetic flux, and EMF is induced into the conductor (generates electricity)

Magnitude or size of induced EMF is determined by what 4 factors?

speed, strength of magnetic field, angle between conductor and direction of magnetic field, and turns in conductor

Speed vs magnitude or size of induced EMF relationship

direct

more lines cut per second, the higher induced EMF

Strength of Magnetic Field vs Magnitude or Size of Induced EMF relationship

direct

the stronger the magnetic field, the higher the induced EMF

Angle between Conductor and Direction of Magnetic Field vs Magnitude or Size of Induced EMF relationship

direct

the less the angle the less induced EMF (because with greater angle, space between lines is smaller and can cut more lines per second)

Turns in the Conductor vs Magnitude or Size of Induced EMF relationship

direct

if the conductor is wound into a coil the lines are additive and will cut more lines (inducing more current)

What do we use to find the direction of induced current?

Left Hand Dynamo Rule or Generator Rule

Heinrich Lenz-Law

the induced current will flow in a direction that opposes the action which induces it

Two basic types of induction

self induction and mutual induction

The two basic types of induction forms...

the basis for transformers, electrical motors and generators

self induction

induction of an opposing EMF in a single coil by its own changing magnetic field

Direct current

flowing in one direction

Alternating current

current flowing in two directions

Opposing EMF is called

Back EMF

Mutual Induction

Process of inducing current flow through a secondary coil by passing a varying current through a primar coil (2 coils)

What is the basis of transformer operation?

Mutual Induction