Magnetism PowerPoint (stopped pg 14)

Magnetic Field

produced by Electric Charges in Motion

Magnetic Field aka

lines of force, lines of flux, magnetic flux

Magnetic flux through a wire is at max when

the plane of loop is perpendicular to the magnetic field

Alternating Current (AC) produces

continuous, expanding and contracting magnetic field

Conventional Current

flows Anode to Cathode

Magnetism

Ability of a lodestone or magnetic material to attract iron, nickel, and cobalt

Ferromagnetic

Magnetic Material

• iron

• cobalt

• nickel

Paramagnetic

Low permeability + weak attraction

• platinum

• aluminum

Diamagnetic

Weakly repelled by both magnetic poles

• beryllium

• bismuth

• lead

Nonmagnetic

Not affected by magnetic fields

• wood

• glass

• rubber

• plastic

Magnetic domain

A group of atoms aligned in the same direction; exhibits a magnetic field

Magnetic field surrounds

magnetic or moving electric current

1 tesla (T)

10,000 gauss (G)

(The Laws of Magnetism)

Repulsion - Atrraction

Like poles repel, opposites attract

(The Laws of Magnetism)

Magnetic Poles

Every magnet has 2 poles, North and South

(The Laws of Magnetism)

Inverse Square Law

Force between 2 magnetic fields

• Directly proportional to the product of their magnitude

• Inversely proportional to the square distance between them

Solenoid

series of looped wire (coil) with current flowing through

Electromagnetic Induction

The production of a current in a conductor by a changing magnetic field

Michael Faraday concluded that voltage, or EMF (electromotive force) could be induced in 3 ways

• Moving a magnet near a stationary conductor

• Moving a conductor near a stationary magnet

• Holding the conductor stationary while generating a magnetic field with a stationary AC magnet

(Electromagnetic Induction)

A bar magnet and a wire loop move with the same linear velocity and direction

the voltage induced in the wire is ZERO

(Factors which affect strength of induced EMF

Faraday’s Law aka First Law of Electromagnets)

Strength of

magnetic field

(Factors which affect strength of induced EMF

Faraday’s Law aka First Law of Electromagnets)

The speed of

motion between the field lines and conductor

(Factors which affect strength of induced EMF

Faraday’s Law aka First Law of Electromagnets)

The angle between

magnetic field lines and conductor

(Factors which affect strength of induced EMF

Faraday’s Law aka First Law of Electromagnets)

The number of

turns in the conducting coil

Lenz’s Law

aka Second Law of Electromagnetics

Induced current sets up a magnetic field opposing the action that produced the original

In other words, that induced current opposes any flux change

Mutual Induction

The result of two coils being placed in close proximity. A varying current is supplied to the first coil, which then induces a similar flow in the second coil

Magnetic fields can

produce electric current

• Induced current in a ware loop results from an alternatively expanding and contrasting magnetic field (AC power)

Self - Induction

• Occurs when alternating current in the coil creates an outward expanding and varying magnetic field

• The changing magnetic field produces an electric field (i.e., current)

Generators aka dynamo

An electromagnetic device that converts mechanical energy into electrical energy

A simple generator is composed of

conductor and magnets arranged

(Generators)

When using AC

• Resistance is calculated in Impedance (Z)

• Electrical production can be graphically expressed in sinusoidal wave

(Generators)

Simple DC generator similar to AC generator except

uses a commutator ring in place of a slip ring

• commutator ring: converts AC - DC (or vice versa)

• slip ring: transfers AC from rotator - stator

(Generators)

Simple AC generator, values of induced voltage in armature loop is maximum when

orientation of armature as compared to the magnetic field is 90 degrees

American generators operate at

60HZ

• AC current change direction 7,200 times in a single minute

Motors

An electromagnetic device used to convert electrical energy into mechanical energy

Components of an induction motor

• Rotor

• Stator

  • Consisting of electromagnets

(Motors)

Motor power can be regulated by

characteristics of electromagnetics that make up the stator

(Motors)

Use multiple

current and can turn at varying rpm

(Motors)

Used to

spin the x-ray tube anode disk