Magnetism/ Electromagnetism

An electromagnet is

temporary magnet created when there is a current in a wire coil

Magnets are classified according to their ____________ when brought into a magnetic field.

Behavior

The movement of electrons in an orbital magnetic moment is called _______ __________ ___________.

Spin magnetic moment

The first law of electromagnetics is

Faraday's law

The second law of electromagnetics is

Lenz's law

The force field created when magnetic dipoles orient are called

Lines of force or lines of flux

The _____-___ and ___________ of alternating current created electricity.

Set-up and collapse

In Direct Current, the electrons flow steadily in a _________ direction or "__________"

Single direction or "forward"

Define the transformer law.

The EMF induced in the secondary coil is to the EMF in the primary coil, as the number of turns in the secondary coil to the number of turns in the primary coil. The relationship is direct.

What are the three laws of magnetism?

1. Every magnet has a north and south pole 2. Like poles repel and opposite poles attract 3. Force of attraction or repulsion varies directly with the strength of the poles and inversely with the square distance between them (inverse square law)

One complete period, with current flow first in one direction and then in the other is called a cycle, and _____ cycles per second. There are ____ alterations, where current flows back and forth in the conductor 120 times in each second.

60 cycles; 120 alterations

Hans Christian Oersted

Discovered that an electric current causes a magnetic field

As the distance decreases, the attraction of the magnet ______________.

Increases

The magnetic force is referred to as

Magnetism

Ferromagnetic is any magnetic material like iron, cobalt or nickel that can become ______________ magnetized.

Permanently

Diamagnetic materials like beryllium actually ______ a magnet although feeble.

Repel

Flux is also referred to as

Zone of influence

A magnetic field is produced by A. Electric charges at rest B. Electric charges in motion C. Permanent magnets only D. None of the above

b. electric charges in motion

Define a generator

converts mechanical energy to electrical energy

What is Eddy current loss?

current that opposes the magnetic field that induced it, creating a loss of transformer efficiency *only occurs with iron in the core (all except air)

Magnetic flux is a product of which two things?

magnetic field strength and the area through which magnetic field lines pass

Define full-wave rectification

the conversion of the opposing half of the incoming electron flow to always move in the same direction, instead of discarding half the cycle

Define ferromagnetic

Materials with very strong magnetic fields

Magnetic flux is defined as moving from __ to __.

N to S

There are three classifications of magnets; _________ (the earth itself, Lodestone), ___________ ______________ (hard steel, artificially magnetized- shaped like a horseshoe), and ___________________ (temporary magnets produced by electric current.

Natural; Artificial permanent; Electromagnet

What is a hysteresis loss?

The property of ferromagnetic materials where the magnetic induction of a coil lags the magnetic field that is charging the coil

Define an autotransformer

Varies the input voltage sent to the primary coil of the step up transformer

The magnetic flux through a wire loop A. Requires a time-varying magnetic field B. Is maximum when the plane of the loop is perpendicular to the magnetic field C. Increases as the magnetic field decreases D. Stays fixed in orientation regardless of electron flow

b. is maximum when the plane of the loop is perpendicular to the magnetic field

A magnet is moved in and out of a coil of wire connected to several lamps. If the number of coils is doubled

it is harder to move the magnet

Define rectification

the process of converting AC to DC

Define a closed core transformer

A transformer with a closed core, directs the lines of force from primary and secondary cores toward each other, resulting in a significant system net increase in field strength.

In which of Fleming's rules, does the thumb indicate the direction of electron current flow, and the fingers indicate the direction of the magnetic field? A. Left Hand Thumb Rule B. Right Hand Thumb Rule

A. Left Hand Thumb Rule

Outside the magnet, the lines of flux travel from: A. north pole to south pole B. south pole to north pole C. east pole to west pole D. west pole to east pole

A. North Pole and South Pole

When two magnetic objects have like poles facing each other, the magnetic forces pushes them _______.

Apart

Magnetic domains are

Clusters of atoms whose spins are aligned (net magnetic field)

A transformer has a ____________ core which in turn amplifies the field of magnetism.

Ferromagnetic core

A loop of wire is referred to as a

Solenoid

Flux density is measured in

Tesla (T) and Gauss (G)

A magnet is moved in and out of a coil of wire connected to a high-resistance voltmeter. If the number of coils doubles, the induced voltage

doubles

The big advantage that AC provides for the power grid is that it is relatively easy to change the __________ of the power, using a device called a _______________.

Voltage; transformer

Each cycle consists of two alterations, voltage starts at ______, rises to a ____________ in one direction, then returns to ______, it then increases to a ____________ in the other direction and then again returns to _____.

Zero, maximum, zero, maximum, zero

Define an electromagnet.

a soft metal core made into a magnet by the passage of electric current through a coil surrounding it.

What is a step down transformer?

a transformer that decreases voltage

What is a step up transformer?

a transformer that increases voltage

Michael Faraday

discovered electromagnetic induction; a voltage would be generated across a length of wire if that wire was exposed to a perpendicular magnetic field flux of changing intensity

Magnetism is defined as the ability of certain materials to attract iron, cobalt, or nickel. True or False?

True

What is a magnetic dipole?

small magnet created by the electron orbit

Define half-wave rectification

suppressed rectification resulting from only half of the incoming alternating current being converted to pulsating direct current; called self-rectification

A solenoid is a ________ dimensional coil that can create controlled magnetic fields and can be used as ________________.

three; electromagnets

In which of Fleming's rules, does the thumb indicate the direction of conventional current flow and the fingers indicate the direction of the magnetic field? A. Right Hand thumb rule B. Left Hand thumb rule

A. Right Hand thumb rule

The greater the magnet size, the better the ____________ or zone of influence.

Attraction

When two magnets or magnetic objects are close to each other, there is a force that ________ the poles together.

Attracts

A magnet is any material that

Attracts certain materials (iron, cobalt, or nickel)

An induced current in a wire loop A. Results from a constant magnetic flux B. Results from an alternately expanding and contracting magnetic field C. Is in such a direction that it's effects oppose the change producing the current D. Always decreases when the magnetic flux decreases

B. results from an alternating expanding and contracting magnetic field.

Inside the magnet, the lines of flux travel from: A. north pole to south pole B. south pole to north pole C. east pole to west pole D. west pole to east pole

B. south pole to north pole

Creating a coil of wire ______________ the field. Wrapping a wire around an iron core greatly increases the ________ of the magnetic field.

Concentrates; strength

Electrons moving in a ___________ are surrounded by a magnetic field and under suitable conditions moving magnetic fields can _________ electron currents.

Conductor; induce

inverse square law applies to A. Magnetism B. Electric field C. Gravity D. All of the above

D. All of the above

As the distance increases, the attraction of the magnet _______________.

Decreases

The factors governing the effectiveness of a solenoid or electromagnet are; the ___________ of the coil, the ________ of the coil and the ____________ passing through.

Diameter of the coil, length of the coil, and the current passing through

Electricity flows in two ways: __________ current or ____________ current.

Direct or alternating current

The difference between AC and DC has to do with the ___________ in which the electrons flow.

Direction

Atoms having a significant number of ___________ with their magnetic moments in the same direction will exhibit a _____ magnetic field in a distinct direction.

Electrons; net

Paramagnetic is magnetic material like platinum that are __________ attracted by a magnet.

Feebly

Flex density can be greatly increased by adding a ___________________ core. Called an electromagnet.

Ferromagnetic

A magnetic field consists of imaginary lines of _______ coming from moving or spinning electrically charged particles.

Flux

The magnetic field on an object can create a magnetic ________ on other objects with magnetic fields.

Force

Magnetism is a fundamental force. When a charged particle is in ________ a magnetic force field _________________ to the motion will be created.

Force; perpendicular

Non-magnetic materials like wood, plastic or glass are not susceptible to magnetic ___________.

Induction

An electromagnet is an object that acts like a ________, but it's magnetic force is created and controlled by __________.

Magnet; electricity

Wrapping insulated wire around a piece of iron and then running electrical current through the wire will make the iron become __________. This occurs because a magnetic field is created when it has electrical current flowing through it.

Magnetized

The strength of the electromagnet is determined by the ________ of loops (turns) of wire, the ________ strength, and the _____________ of the core.

Number; current strength; permeability

In Alternating Current, the electrons keep ___________ directions, sometimes going "__________" and then going "____________"

Switching; "forward" and then going "backward"

Lines of Flux, lines of force, magnetic field

The force field that are created when magnetic dipoles orient to create a magnet

In AC, the current reverses or alternates, ___ times per second for 1 full cycle or phase.

60xsec

In AC, the power that is available at a wall socket is ____- volt, 60- cycle AC power.

120- volt

State the factors that regulate the strength of electromagnetic induction.

1. Strength of the current 2. Permeability of the core 3. The number of turns in the conducting coil

List the types of movement that will produce electromagnetism.

1. Move the conductor through a stationary unchanging strength magnetic field. 2. Move magnetic lines of force through a stationary conductor with an unchanging strength magnetic field. 3. Vary the magnetic flux strength from a stationary magnet through a stationary conductor. As the flex strength varies, the lines of force will expand and contract, in effect causing the relative motion necessary to induce current.