Electromagnetism Flashcards by Emily Mott

A variable resistor to control current

Rheostat

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The magnetic effect of electrocurrent was discovered by:

Oersted

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Current is created by the flow of ____ from a negative terminal to a positive terminal

electrons

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Current behaves as if ____ charges cause the flow

positive

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The configuration of a coiled wire

solenoid

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T/F: If you add an iron core to the solenoid, it will refine and organize the magnetic field even further.

True

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Law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force

Faraday’s Law of Induction

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Measures magnitude and direction of electric current

Galvanometer

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An electric current is induced in a circuit if some part of that circuit is exposed to a changing magnetic field. The current this produces is:

Alternating current

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Increasing the number of coils being affected by the magnetic field [increases/decreases] the voltage induced in the coils

Increases

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If you double the number of coils being affected by the magnetic field, the voltage:

Doubles

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Doubling the strength of the magnet will ____ the induced voltage

Double

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Also, increasing the coil’s speed of motion through the field will [increase/decrease] the strength of the field

increase

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If the motion of the wire is placed ____ to the magnetic field, the highest number of flux lines will interact with the wire causing the greatest current available.

Perpendicular

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If the motion of the wire is at an ____ angle, then the current will be less as fewer lines of magnetic force will affect the wire over the same period of time

Oblique

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The magnitude of the induced current depends upon:

1.The strength of the magnetic field
2. The velocity of the magnetic field as it moves past the conductor (wire)
3. The angle of the conductor to the magnetic field
4. The number of turns in the conductor (coils)

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Happens when an uncharged metallic object experiences a shift in electrons when it is brought into the electric field of a charged object

Electric induction

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The generation of an induced current that opposes any change in current existing in the circuit whether it an increase or decrease.

Self induction

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The generation of an induced alternating current in a secondary coil by supplying an alternating current to a primary coil

Mutual induction

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____ always opposes the changing current

Self induction

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This process occurs when the alternating current within the induced circuit creates its own magnetic field that induces a second current to flow within the wire, but in the opposite direction

Self induction

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Two types of electromagnetic induction:

Self induction, mutual induction

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According to ____, an induced current flows in the opposite direction of the magnetic field change that produced it

Len’z law

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T/F: It is not necessary to physically move a magnet near a coil to induce an electric current.

True

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Can produce an electric current by rotating loops of wire in a fixed magnetic field

Magnetic generator

Coils of wire used in a magnetic generator in place of a single loop of wire

Armature

Solid round ring used to generate AC power

Slip ring

Rings with two open slits aligned at a plane 90 degrees perpendicular to the plane of the loop (changes AC to DC)

Commutator ring

Mechanism where an electric current is supplied to the loop instead of mechanical energy

Electric motors

Several fixed electromagnets arranged in pairs

Stator

located in the middle of the stator and composed of an iron core surrounded by coils

Rotor

Changes currents and electric potential into higher or lower intensities

Transformer

3 types of transformers:

Closed core, shell type, auto transformer

Transformer that increases voltage

Step up transformer

Study of stationary charges

Electrostatics

Electric fields radiate toward a ____ charge

Negative

The study of moving electric charges

Electrodynamics

A region around a charged particle within which it can exert a force or have a force exerted upon it by other charged particles

Electric fields

The force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.

magnetism

Particles with opposite charged electric fields attract each other as positive charges will have electrical field lines going out of it, and negatively charged particles will have electrical field lines coming towards it. These are called:

Monopoles

In magnetic materials, orbiting electron spin in one direction. Electrons spinning in one direction in this manner create tiny magnetic fields called ____ with a North Pole and a South Pole

Dipoles

when a number of these dipoles (atomic magnets) align with each other, they create a grouping called a:

Magnetic domain

Magnetic fields consist of lines of force in space called a:

Flux

a measurement of the total magnetic field which passes through a given area. It’s created when magnetic dipoles orient in one direction to create a magnet

Magnetic flux

Unit of measurement for magnetic field strength is the:

Tesla (T)

T/F: Any charged particle in motion creates a magnetic field

True

The magnetic field is ____ to the motion of the particle

perpendicular

A magnetic field is a ____ loop moving with the charged particle

closed

3 basic types of magnets:

natural magnets, artificial permanent magnets, electromagnets

Natural magnets are also called:

Lodestones

Manufactures magnets:

Artificial permanent magnets

In its simplest form, it is an iron bar wrapped with a wire carrying an electric current

Electromagnets

Weakly repelled by magnetic fields (water, mercury, gold, etc.)

Diamagnetic

Not affected by magnetic fields (wood, glass, plastics, etc.)

nonmagnetic

those weakly attracted to magnetic fields (plutonium, gadolinium, aluminum, etc.)

Paramagnetic

materials that are strongly attracted to magnetic fields (iron, cobalt, nickel, etc.)

Ferromagnetic

Two ways to induce a magnetic field:

Placing the material in a magnetic field; Rubbing the material against a permanent magnet

The electric current through an X-ray tube is measured in:

milliamperes

For an electric current to flow through a conductor, the electrons must be driven by:

A potential difference

When a charged particle moves in a straight line, a magnetic field is created ____ to the particle motion

perpendicular

The term electromagnetic induction refers to the production of:

An electric current

The force between the poles of two bar magnets varies [x] with the distance between them

directly

The fact that an electric current is induced if the conductor is in a changing magnetic field was discovered by:

Faraday

The experimental link connecting electric and magnetic forces was first discovered by

Oersted

When the right-hand rule is applied to a straight wire, the thumb indicates the direction of the:

Electric current

T/F: Most magnets are still magnetic when broken.

True

T/F: Most magnets are affected by another magnetic field.

True

If two magnets are bought together, north-to-north poles will [a], whereas north- to-south poles will [b]

repel; attract

Given a closed loop of wire with no electron flow, an electric current can be induced if:

A changing magnetic field is present

To make an electromagnet stronger, a coil of wire is [x] an iron core.

wound around

A difference between self-induction and mutual induction is that mutual induction requires [a] coils and self- induction requires only [b].

two; one

The ability of an element in a circuit to reduce or imped the flow of electricity defines:

Resistance

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

at the area of the greatest curvature of the conductor

Electrification by induction requires that the two objects:

are not at all in contact with each other

Magnetic fields consist of lines of force known as ____

Flux lines

An electric current produces a magnetic field that is __________ to the direction of the current

perpendicular

T/F: Magnetic fields extend infinitely becoming weaker the further they travel away from their source

False

Electric fields radiate out from a ____ charge

positive

The study of moving electric charges typically focuses on the movement of:

Electrons

Magnetism is the ability of certain materials to attract:

iron, cobalt, or nickel

T/F: Magnetic flux travels from north to south inside a magnet.

False

According to the laws of magnetism, how will the north pole of one magnet react to the south pole of another magnet if placed very close together?

They will attract

Water is magnetically classified as which of the following?

Diamagnetic

T/F: A stronger magnetic field will magnetize a ferromagnetic material more strongly.

True

What is the right-hand rule used to determine?

Direction of magnetic flux

The induction of a “back” current within the same coil is called:

Self-induction

Transformer that decreases voltage

Step-down

A type of transformer in which the coils are wound around a square or circular core to provide a continuous path for the magnetic field; it is insulated to help contain and direct the magnetic force lines.

Closed-core

The most commonly used transformer; it "traps" the magnetic forces more efficiently in order to induce the strongest possible current in the secondary coil.

Shell transformer

A device that raises or lowers voltage in the primary circuit, depending on the setting chosen on the machine's control panel for the kilovolt peak voltage (kVp)

Autotransformer

Moving a conductor by manual means within a magnetic field is the basic operation of a:

Generator

T/F: The commutator ring in a generator design briefly breaks contact between the armature and circuit.

True

What is the fundamental design difference between a generator and motor?

Electricity is applied to the armature of a motor.

The external magnets of an induction motor are called:

Stators

Basic transformer operation is based on what principle?

Mutual induction

Which transformer design operates by self-induction?

Autotransformer

In which device does a commutator ring serve to feed current through an armature the same direction each time?

Motor

Converting mechanical energy to electrical energy is the purpose of which device?

Generator

Transformers operate best with:

Direct current