MRI PRELIMS Q2

Electrodynamics

The science of electric charges in motion.

Electric Current

The flow of electric charge through a conductor.

Closed Circuit

A complete path that allows electric current to flow.

Open Circuit

A broken path where electron flow stops.

Barricade in a Conductor

Any obstruction that stops electron flow and current.

Ampere (A)

The SI unit of electric current; 1 A = 1 coulomb per second.

Electric Potential (Volt)

The force that drives electrons through a circuit.

Electric Resistance (Ohm)

The opposition to the flow of electric current.

Electric Power (Watt)

The rate at which electrical energy is used or work is done.

Direct Current (DC)

Electric current flowing in only one direction.

Battery

A source of direct current.

Alternating Current (AC)

Electric current that periodically changes direction.

Phase

A condition where electrons move in the same direction with the same velocity.

Ohm’s Law

The voltage across a circuit equals the current multiplied by the resistance.

Impedance

The opposition to current caused by collisions within a conductor.

Resistive Impedance

Opposes current and converts electrical energy into heat.

Inductive Impedance

Stores energy in a magnetic field when current flows.

Capacitive Impedance

Stores electrical energy as an electric field.

Resistive Heating

The conversion of electrical energy into heat within a device.

Insulator

A material that resists the flow of electrons.

Quartz

An example of an insulator.

Rubber

An example of an insulator.

Glass

An example of an insulator.

Diamond

An example of an insulator.

Conductor

A material that allows electrons to flow easily.

Copper

An example of a conductor.

Aluminum

An example of a conductor.

Silver

An example of a conductor.

Gold

An example of a conductor.

Silicon

An example of a semiconductor.

Germanium

An example of a semiconductor.

Superconductor

A material with zero electrical resistance at extremely low temperatures.

Magnetism

A field effect related to moving electrons in certain materials.

Lodestone

The first known natural magnet.

Magnetic Domain

The smallest region of magnetism containing north and south poles.

Magnetic Domain Strength

Depends on the number and alignment of magnetic domains.

Electron Configuration

The arrangement of electrons around an atom’s nucleus.

Magnetic Susceptibility

The degree to which a material becomes magnetized in a magnetic field.

Ferromagnetism

Easily magnetized materials with susceptibility greater than 1.

Iron

A ferromagnetic material.

Nickel

A ferromagnetic material.

Cobalt

A ferromagnetic material.

Paramagnetism

Weakly magnetized materials with susceptibility less than 1.

Aluminum

A paramagnetic material.

Gadolinium

A paramagnetic material.

Diamagnetism

Materials with negative susceptibility that are slightly repelled by magnets.

Water

A diamagnetic material.

Magnetic Dipole

A magnetic region with both a north and south pole.

Law of Magnetism

A magnet cannot exist with only one pole.

Attraction and Repulsion

Like poles repel and unlike poles attract.

Magnetic Induction

The process of making a nonmagnetic material magnetic.

Magnetic Lines of Induction

Lines representing magnetic field strength and direction.

Magnetic Permeability

The ability of a material to allow magnetic field lines to pass through.

Electromagnet

A magnet produced by electric current flowing through a conductor.

MRI Electromagnet

Uses electric current to produce magnetism during operation.

Gauss’s Law (Magnetism)

The interaction of magnetic fields proportional to magnetic poles.

Magnetic Field

A region around a magnet where magnetic forces act.

Tesla (T)

The SI unit of magnetic field strength.

Gauss (G)

The older unit of magnetic field strength.

Tesla to Gauss Conversion

1 Tesla equals 10,000 Gauss.