Exam 2

Instrument used to detect magnetic direction

Compass needle

What happens to a compass needle when AC current reverses direction

Needle flips direction

1 tesla = ____ gauss

10,000

What happens to magnetic field strength as distance from the electromagnet increases

It decreases

Instrument used to measure magnetic field strength

Field meter

Unit used to measure magnetic field strength

Gauss (G)

Relationship between electromagnet distance and field strength

Inverse

What increasing the number of wire loops in an electromagnet does to magnetic field strength

Increases field strength

Electromagnet component that strengthens magnetic flux by repeated loops

Coil

Relationship between number of loops and magnetic field strength

Direct relationship

What decreasing AC wavelength causes

Increased frequency

Number of cycles per second in alternating current

Frequency

Relationship between wavelength and frequency

Inverse relationship

Effect of increasing AC frequency on magnetic field reversals

More rapid reversals

Effect of decreasing AC wavelength on magnetic field behavior

Faster oscillation of magnetic field

What determines how often the magnetic field changes direction in AC

Frequency

What creates a magnetic field around a conductor

Moving electric current

Direction of magnetic field relative to current flow

Perpendicular

Type of magnet created by electric current through a conductor

Electromagnet

Factor that affects electromagnet strength besides current

Number of loops

Factor that affects electromagnet strength besides loops

Distance from source

Ability of certain materials to attract ferromagnetic substances

Magnetism

Substances that are strongly attracted by magnets, including iron, nickel, and cobalt

Ferromagnetic substances

Invisible region surrounding a magnet where magnetic forces act

Magnetic field

Another term for magnetic field

Magnetic force

Invisible lines that represent the magnetic field

Lines of force

Another name for lines of force

Lines of flux

The property of a magnetic field that indicates the path and strength of magnetic force

Magnetic flux

Law stating that the strength of a magnetic field decreases as distance increases

Inverse square law

The two ends of a magnet where magnetic force is strongest

Magnetic poles

Law stating unlike poles attract each other

Magnetic attraction

Law stating like poles repel each other

Magnetic repulsion

Direction magnetic flux lines travel outside a magnet

North to South

Magnetic field lines that form an unbroken path

Continuous loops

The characteristic of magnetic flux lines that means they always reconnect and never end

Closed loops

What magnetic flux lines never do when interacting with one another

Intersect

The concentration of magnetic field lines in a given area

Flux density

What closely spaced magnetic flux lines indicate

Strong magnetic field

What widely spaced magnetic flux lines indicate

Weak magnetic field

SI unit used to measure magnetic flux density

Tesla (T)

Approximate magnetic field strength of a refrigerator magnet

0.1 Tesla

Approximate magnetic field strength of the Earth

0.0001 Tesla

Process by which a magnetic property is produced in an object by placing it in a magnetic field

Magnetic induction

Temporary magnetization caused by exposure to a magnetic field

Artificially induced magnet

Magnets formed naturally in nature

Natural magnets

Magnets manufactured to retain their magnetic properties

Artificial permanent magnets

Magnets created by electric current flowing through a conductor

Electromagnets

What every charged particle in motion creates

Magnetic field

Flow of electric charge through a conductor

Current

The two types of electric current

Direct current (DC) and alternating current (AC)

Type of current that flows in only one direction

Direct current (DC)

Type of current that periodically reverses direction

Alternating current (AC)

Type of magnetic field produced by direct current

Constant magnetic field

Type of magnetic field produced by alternating current

Changing magnetic field

How often alternating current changes direction per second

Frequency

Factor in alternating current that affects the magnetic field strength and behavior

Frequency

Name of property that is the strength of magnetic attraction or repulsion

Magnetic force

What happens to magnetic flux lines when exposed to another magnet

They are affected or distorted by external magnetic fields

What happens when flux lines run opposite to one another

They attract

Basic characteristic of all magnetic fields showing they have no beginning or end

Closed-loop nature

The direction and amount of force present in a magnetic field

Direction and magnitude

Material often mistaken as magnetic but not always attracted to magnets

Stainless steel

Move ________ lines of flux across a conductor _____ a current

magnetic, induces

Move a ________ through a stationary magnetic field ____ a current

conductor, induces

Vary the strength of a stationary magnetic field through a conductor, how?

using an electromagnet and varying the current running through it. Using AC (Alternating current)

A helical coil of wire whose length is substantially greater than its diameter, used to create a magnetic field

Solenoid

A device that uses a conductor, a core, and a current source to produce a magnetic field

Electromagnet

A conductor carrying current will produce this, oriented perpendicular to the direction of current flow

Magnetic Field

If current is constant, this remains constant; if current varies, this varies

Magnetic Field

An electric current is induced in a circuit when some part of that circuit is in one of these

Changing Magnetic Field

The three required components for electromagnetic induction

1. Magnetic Field

2. Conductor

3. Relative motion

The scientist credited with discovering electromagnetic induction

Michael Faraday

The process where a magnetic field causes the production of a voltage across a conductor, which in turn causes an electrical current

Electromagnetic Induction

The rule that dictates an electric current is induced in a circuit if some part of that circuit is in a changing magnetic field

Faraday’s Law of Induction

An electromagnet used to convert mechanical energy into electrical energy

Electric Generator

The relationship between magnetic field and current when the current remains steady

Constant magnetic field

The relationship between magnetic field and current when the current changes

Varying magnetic field

Method of induction involving the physical displacement of magnetic flux across a wire

Moving magnetic lines of force across a conductor

Method of induction involving the physical displacement of a wire through a non-moving field

Move a conductor through a stationary magnetic field

Method of induction involving a pulsating magnetic field through a stationary conductor

Self induction

A rule used to determine the direction of magnetic field lines around a conductor carrying a current

Fleming’s Right Hand Rule

Common examples of electromagnets found in imaging equipment

Rotor/Stator, Detente locks, Circuit breakers

Does the frequency of the alternating current affect the strength of the magnet?

Yes

The MRI images rely on the protons within the _______ atom.

Hydrogen

It would be safe to take a patient with an insulin pump into MRI Zone 4?

No

Electromagnetic Induction requires all of the following except ……

Electricity

Which of the following will influence the magnitude of an induced current?

Strength of magnetic field, speed of motion, and number of turns of the conductor

What effect does adding an iron core have on an electromagnet's field strength?

The magnet is stronger

Unit of Electromotive force (EMF)

Voltage or volts

Unit of mechanical force

Newtons

What are the 3 main things electromagnets are used in imaging

1. Induction motor

2. Detente locks

3. Circuit breakers

Four factors of Faraday’s law to change magnitude of induced current

1. Strength of magnetic field

2. Speed of motion between lines of force and conductor

3. Number of turns of the conductor

4. Angle between lines of flux and conductor

How does a generator produce electricity

Converting mechanical energy into electrical energy using electromagnetic induction

What does electric induction do?

When you take a neutral object and charged object, the neutral objects charges get redistributed and become charged without direct contact

What is magnetic induction?

Orienting a ferromagnetic materials dipoles in the same direction as the external magnetic field, causing temporary magnetism

What does electromagnetic induction do?

Creates electricity using a magnetic field

The induced current is highest when the conductor and magnetic field are ____

perpendicular

State and explain one of faraday’s four factors that influence the magnitude of induced current

The speed of motion influences the magnitude of induced current. The faster this movement occurs, the more magnetic field lines are "broken" or crossed per second.

Describe the three basic methods to induce a current in a conductor

1. Moving a magnet near the conductor

2. Moving the conductor in a magnetic field

3. Changing the strength of the magnetic field

The result of moving a magnet near the conductor

Moving the magnet in creates a current in one direction, while pulling it out creates a current in the opposite direction