Unit 4- Electric and Magnetic Fields

Electrostatics

The study of stationary electric charges and the forces and fields associated with them.

Electrodynamics

The study of the behavior of electrically charged particles in motion and the forces acting on them.

Electrification can occur by

contact, friction, or induction

Coulumb's Law

-Bigger Charges means stronger bonds

-The closer the bonds the stronger the bonds

Conductor Distribution

On the external surface of the object

Non-Conductor Distribution

Throughout the object

Where do charges concentrate

On the outer curvature of the object

Potential or EMF name

Voltage (V)

Charges in motion = Electric current which is

amperage (measured in amperes or amps (A))

Conductor

a material that allows electricity to flow through it easily

Semi Conductor

element that does not conduct electricity as well as metal but conducts better that a nonmetal

Superconductor

A material that has no electrical (e-) resistance.

Insulator

A material in which electrons are not able to move easily

Potential Electric Circuit

A build-up of charges with the potential to cause them to move

-Measured in Volts

What is the fllow of charges (Current) measured in?

Amperes (A)

What is Resistance in Electricity?

Anything that inhibits electron movement

What is resistance measured in?

Ohms (Ω)

What 4 factors does resistance depend on?

1) Material

2) Length

3) Diameter

4) Temperature

As length goes up, resistance

goes up

As diameter goes up, resistance

goes down

As temperature goes up, resistance

goes up

3 Properties in Ohm's Law

Volts (V)

Amps (I)

Resistance (R)

Direct Current

an electric current that flows in one direction steadily

One direction from the neg. pole/electrode to pos. pole/electrode

Alternating Current

A flow of electric charge that regularly reverses its direction.

USA AC Frequency Cycles

60 Hz

Series Circuit

A circuit in which all parts are connected end to end to provide a single path of current.

Parallel Circuit

A circuit that contains more than one path for current flow.

Battery definition

a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power.

Capacitor definition

- Store energy and charge by holding electrons on plates separated by a very small distance

- Represented as ||

Diode definition

A component that allows current to flow in one direction only.

Circuit Breaker definiton

protective devices that "break"the circuit when a sudden high increase incurrent occurs.

Resistor defintion

inhibits electron flow thus regulating current

Switch definition

A device for making, breaking, or changing the connections in an electrical circuit.

Transformer definition

mechanism used in an electrical circuit to increase or decrease the voltage.It can be step-down or step-up or auto transformer type

Grounding

The Earth is considered an infinite reservoir of electrons therefore any charged object can be “neutralized” (brought to a state of no charge) by connecting it to the Earth by a conductor.

Electromagnetism definition

"the branch of physicsthat deals with the relationship betweenelectricity & magnetism"

What do magnetic field lines represent?

The strength and direction of a magnetic field

Magnetic fields are always

closed loops

Orbital Magnetic Moment

the motion of a charged particle creates a magnetic force field perpendicular to the motion

Spin Magnetic Moment

electron rotation on an axis

Magnetic Dipole

small magnet created by the electron orbit mostly moving in one direction

Magnetic Domain

When multiple magnetic dipoles arealigned in a parallel fashion and add to theoverall effect

Magnet

When most magnetic domains align to create a fieldthat is observable.

Magnetic force intensity is ___ proportional to the product of pole strengths

Directly

Magnetic force intensity is ___ proportional to the density of the flux lines (number of lines in the area)

Directly

Magnetic force intensity is ____ proportional to the square of the distance between the poles

inversely

Nonmagnetic

Unaffected by a magnetic field

Diamagnetic

weakly repelled by a magnetic field.

Paramagnetic

weakly attracted to a magnet

Ferromagnetic

strongly attracted to a magnetic field

Magnetic Permeability

ability of a material to become magnetized

Magnetic Retentivity

the ability of a material to stay magnetized

Electromagnets

A type of magnet whose magnetic field is produced by the flow of electric current.

Solenoid

a coil of wire with an electric current in it

Difference between a solenoid and electromagnet

Electromagnet is a solenoid with a ferromagnetic core

3 ways to accomplish induction

1)Magnetic Field is moving

2)Magnetic Field is changing/ varying

3)Conductor is moving

Magnitude of Current

1) Proportional to strength of magnetic field

2) Proportional to velocity/speed/ frequency

3) Proportional to angle of the conductor

4) Proportional to the # of loops

Primary Solenoid

has a growing then collapsing magnetic field that then reverses and repeats this as the AC cycles.

Secondary Solenoid

a coil of wire, usually surrounding a primary solenoid or part of a dual-coil setup, that becomes a magnetic source due to a changing magnetic field generated by the primary coil through electromagnetic induction.

Generator

A machine that converts mechanical energy into electrical energy

Motor

Changes electrical energy into kinetic/mechanical energy

Induction Motor

Powers the rotating anode of an x-ray tube

The primary side of the transformer is supplied with

electricity

The secondary side of the transformer is supplied with

Current

Step up Transformer

increases voltage and decreases current

Step down Transformer

decreases voltage and increases current

Voltage is ___ proportional to the turn #

Directly

Voltage is ___ proportional to current

Inversely

Eddy Current Losses

-These are currents that are induced in the ferromagnetic core which produces heat thus losing energy

-Decreased by the material used in the core and volume of the core material.

Hysteresis Losses

-Constant reversal of the magnetic fields in the core produces heat thus losing energy.

-Decreased by lamination of the core material

Copper Losses

-Resistance in the conductor material of the windings/turns leading to heat &energy loss.

-Decreased by decreasing resistance in the conductor windings, typically by increasing the diameter of the conductors.

Closed- Core Transformer

built around a square core of ferromagnetic material

Shell Type Transformer

converges the inside and outside lines of force through an iron core. (Secondary Windings)

Autotransformer

serves as a voltage compensator that corrects for minor fluctuations in the current

Electrification can occur by

contact, friction, or induction

Conduction Band

the range of energy levels in a solid where electrons are free to move and conduct electricity.

A material that has a large number of free electrons is ___?

a good conductor.

If a conductor is curved, the greatest amount of charge will be found where?

on the outer surface of the curve

Rubbing a rubber rod with fur is an example of electrification by

friction.

The volt is a unit of measurement for

electric potential difference.

The ampere is a unit of measurement for

electric current.

A battery produces what type of current?

Direct current (DC)

Ohm’s law can be written as

V = I × R where V is voltage, I is current, and R is resistance.

When a switch is turned on, the electric circuit

is closed

Inside the magnet, the lines of flux travel from

the south pole to the north pole.

With mutual induction, to induce voltage in the secondary coil, there must be what?

Alternating current in the primary coil.