Module 5 - Magnetism and Electromagnetism

Magnetism Definition

The polarization of a material

Magnets Definition

Matter that has the ability to attract

Magnetic Field Definition

A vector field that describes the magnetic influence on an electric current

Caused by a moving charged particle

Magnetic Domain Definition

When groups of magnetic fields are spinning in the same direction

Natural Magnets Definition

Magnets that occur naturally

Permanent Artificial Magnets Definition

Magnets that are man-made

Electromagnet Definition

Made by wrapping a coil of wire carrying a current (solenoid) around an iron core

Solenoid Definition

Coil of wire carrying a current

Dipole Definition

Something that has 2 poles, a North and a South

Nonmagnetic Definition

These materials are NOT affected by a magnetic field (have NO attraction to magnets)

Diamagnetic Definition

These materials are weakly repelled from both poles of a magnetic field (repelled by magnets)

Paramagnetic Definition

Materials that are weakly attracted to both poles of a magnetic field (slight attraction to magnets)

Ferromagnetic Definition

Can be strongly magnetized, has a very strong attraction to magnets (strongly attracted to magnets)

Permeability Definition

The ease with which a material can become magnetized

Retentivity Definition

The ability of an object to retain its magnetism

Magnetic Flux Definition

The amount of magnetic field in a certain area

Electromagnetism Definition

The interactions of Electric Currents with Magnetic Fields

Self-Induction Definition

What occurs when there is a single wire/conductor that will be able to induce voltage on itself when the current changes direction

Mutual Induction Definition

What occurs when there are 2 wires/conductors where the primary wire supplied with AC current will induce a current to flow on the secondary wire

Found in transformers

Transformer Defintion

A device that will change Voltage and Current into increasing and decreasing values

Autotransformer Definition

A transformer that has one winding and varies the voltage and current

This type of transformer works off the principle of self-induction

This is found in our operating control console

It is supplied with AC

Closed-Core Transformer

A square core of ferromagnetic material

This type of transformer works off the principle of mutual induction

The primary side is supplied with AC

Shell-Type Transformer

Essentially 2 Closed-Core Transformers with a center post that contains both the primary and secondary windings

This type of transformer works off the principle of mutual induction

The primary side is supplied with AC

This is the most efficient type of a transformer there is

It is also the most common type of transformer used in radiology imaging systems

Stators Definition

Stationary Electromagnets that have AC current supplied to them

Rotor Definition

Center rod that turns, NOT supplied with current, a current is induced in the rotor

Electromechanical Devices Definition

Devices with Electrical and Mechanical processes that came about as a result of Oersted’s and Faraday’s Experiments

What is the SI unit for Magnetic Flux

Weber

What is the traditional unit of measure for Magnetic Flux

Maxwell

1 Maxwell =

1 × 10 ^-8 Webers

What is the SI unit of measure for Magnetic Strength

Tesla

What is the traditional unit of measure for magnetic strength

Gauss

10,000 Gauss =

1 Tesla

What is an example of a natural magnet

Magnetite AKA Lodestone, Leading Stone

Natural Ore

Earth

What is an example of a Permanent Artificial Magnet

Made of: Iron, Cobalt, Nickel

Examples: Refrigerator magnets

Horseshoe shaped magnets

What 2 places in Radiology use Electromagnets

Our detent locks on our tubes are electromagnets

MRI uses a GIANT electromagnet

Examples of nonmagnetic material

Wood

Glass

Examples of Diamagnetic Material

Water

Plastic

Bismuth

Beryllium

Examples of Paramagnetic Material

Gadolinium

Platinum

Examples of Ferromagnetic Material

Iron

Nickel

Cobalt

What is considered to be the best artificial magnet

Alnico

What 3 materials is Alnico made from

Aluminum (Al)

Nickel (Ni)

Cobalt (Co)

What are 2 advantages of an electromagnet

We can control the strength of an electromagnet

We can turn an electromagnet on and off

What are the two types of induced currents

Self-Induction

Mutual Induction

What are the three classifications of magnets

Natural

Permanent Artificial Magnets

Electromagnets

What are the 4 laws of magnets

1. Magnets are dipolar

2. Like charges repel and opposite charges attract

3. The Law of Magnetic Induction- the stronger the magnet is, the stronger the attraction will be

4. The Law of Magnetic Force- The more distance there is between the magnet and an object, the less force there will be

What are the 5 natures of magnets

1. Breaking a magnet in half produces 2 smaller magnets

2. Hammering or heating a piece of steel while it is close to a magnetic field will cause the piece of steel to become a magnet

3. Heating or hammering a magnet close to a magnetic field will cause the magnet being heated or hammered to become unmagnetized

4. Stroking a metal bar repeatedly with a magnet will cause the metal bar to become magnetized

5. Any charged particle in motion will create a magnetic field perpendicular to the motion

What are the four factors that affect the induced current

1. Strength of the magnetic field

2. Speed of the magnetic field

3. The angle of the conductor to the magnetic field

4. The number of turns on the conductor

The stronger the magnetic field is the — the induced current will be

Stronger

The faster the magnetic field moves past the conductor the — the induced current will be

Stronger

The induced current is stronger when the magnetic field lines and the conductor are at or closer to a — degree angle

90 degree angle

The more turns there are on a conductor the — the induced current will be

Stronger

What are the 4 magnetic states of matter

Nonmagnetic

Diamagnetic

Paramagnetic

Ferromagnetic

In a step-up transformer: There are — turns on the primary side

Fewer

In a step-up transformer: There are — turns on the secondary side

More

In a step-up transformer: Voltage — on the secondary side

increases

In a step-up transformer: Amperage — on the secondary side

decreases

What transformer is this?

Step-Up Transformer

What are the AKAs for a Step-Up transformer

High-Tension Transformer

High-Voltage Transformer

In a step-down transformer: there are — turns on the primary side

More

In a step-down transformer: there are — turns on the secondary side

Fewer

In a step-down transformer: Voltage — on the secondary side

Decreases

In a step-down transformer: Amperage — on the secondary side

Increases

What transformer is this?

Step-Down Transformer

What are the AKA’s for a Step Down Transformer

The Filament Transformer

What transformer is this

Autotransformer

What transformer is this?

Closed-Core Transformer

What type of transformer is this

Shell-Type Transformer

Which type of transformer works on the principle of self-induction

Autotransformer

Which types of transformers work on the principle of mutual induction

Closed-Core Transformers

Shell-Type Transformer

Which type of transformer is the most efficient

Shell-type transformer

Which type of transformer is used in the operating control console

Autotransformer

Which type of transformer is the most commonly used in radiology imaging systems

Shell-Type Transformer

What is the turns ratio equation?

Ns/Np

In a turns ratio equation, how would you know if a transformer is a step-up transformer or a step down transformer

If the turns ratio is greater than 1, it is a step-up transformer

If the turns ratio is less than 1, it is a step-down transformer

For the Transformer Law: What is the equation if looking for Voltage and given the number of turns

Vs/Vp = Ns/Np

For the Transformer Law: What is the equation if looking for Amperage and given the number of turns

Is/Ip = Np/Ns

For the Transformer Law: What is the equation if looking for voltage or amperage and the number of turns is NOT given

Is/Ip = Vp/Vs

What is the purpose of a transformer

To change voltage and current into increasing and decreasing values

What is the purpose of an electric motor

Converts electrical energy into mechanical energy

What is the purpose of an electric generator

Converts mechanical energy into electrical energy

What is the purpose of an induction motor

To use electric current to make a rotor turn/rotate

Where is the induction motor used

In the X-ray tube

Which part of the induction motor is fixed/stationary

Stators

Which part of the induction motor turns

Rotor

Which part of the induction motor is supplied with AC

Stators

What type of relationship exists between permeability and retentivity

Inverse Relationship

Magnetite AKA

Lodestone

Leading Stone

Faradays Law AKA

Law of Electromagnetic Induction

Step-Up Transformer AKA

High-Tension Transformer

High-Voltage Transformer

Step-Down Transformer AKA

Filament Transformer

Turns AKA

Windings

Taps

Coils

Electric Generator AKA

Dynamo

A Danish physicist was the first scientist to link electricity and magnetism together.

He took a wire and placed a compass near the wire and ran an electric current over the wire and noticed the compass had moved

He proved that electricity could create a magnetic field

Oersteads Experiment

This experiment went off of Oersted’s Experiment to see if magnetic fields could generate an electric current

An electric current will flow in a circuit as long as some part of the circuit is in a changing magnetic field

Faradays Law