Chapter 4 – The X-ray Circuit & Fundamental Electricity

Vocabulary flashcards covering fundamental electrical and x-ray circuit concepts, devices, and laws presented in Chapter 4. Suitable for English-language study and review.

Electrostatics

The study of stationary electric charges.

Conductor

Material with many free electrons that permits easy flow of electricity.

Insulator

Material with tightly bound electrons that resists the flow of electricity.

Law: Like Charges Repel

In electrostatics, identical charges push apart while unlike charges attract.

Law: Coulomb’s Force

Electrostatic force ∝ (product of charges)/(distance²) between them.

Law: Charge on Surface

Electric charges reside only on the external surface of conductors.

Electrification

Process of adding net positive or negative charge to an object by friction, contact, or induction.

Electrodynamics

The study of electric charges in motion (electricity).

Electric Potential

Ability to do work because of charge separation; measured in volts.

Current

Flow of electrons in a conductor; measured in amperes.

Resistance

Property of a circuit element that impedes current; measured in ohms.

Ohm’s Law

V = I × R; voltage equals current times resistance.

Direct Current (DC)

Electric current that flows in only one direction (e.g., batteries).

Alternating Current (AC)

Current that reverses direction cyclically as source potential changes (house power).

Series Circuit

Circuit with elements wired along a single path; current is equal throughout.

Parallel Circuit

Circuit with elements branching across a conductor; voltage same across all branches.

Battery

Device that produces electrons chemically, stores charge long-term, and provides potential.

Capacitor

Component that temporarily stores an electric charge.

Diode

“One-way valve” that allows electrons to flow in only one direction.

Fuse

Protective device that melts to open the circuit during a surge.

Circuit Breaker

Resettable protective switch that opens the circuit during excess current.

Resistor

Component that deliberately inhibits electron flow to regulate current.

Rheostat

Variable resistor used to adjust current (e.g., mA selector).

Switch

Device that opens or closes an electric circuit pathway.

Transformer

Electromagnetic device that raises or lowers AC voltage by induction.

Grounding

Connecting a device to earth to neutralize charge and enhance safety.

Magnetism

Ability of material to attract iron, cobalt, or nickel due to aligned electron spins.

Magnetic Dipole

Tiny atomic magnet created by electrons spinning predominantly one direction.

Magnetic Domain

Group of atoms with aligned dipoles acting together as a larger magnet.

Magnetic Flux

Imaginary lines representing a magnetic field; travel S→N inside, N→S outside magnet.

Tesla (T)

SI unit of magnetic field strength; MRI systems operate ~0.5–5 T.

Nonmagnetic Material

Substance not attracted to magnetic fields (e.g., glass, wood).

Diamagnetic Material

Material weakly repelled by magnetic fields (e.g., water, mercury).

Paramagnetic Material

Material weakly attracted by magnetic fields (e.g., platinum, gadolinium).

Ferromagnetic Material

Substance strongly attracted to magnets (e.g., iron, cobalt, nickel).

Electromagnetism

Relationship where moving electrons create magnetic fields and moving magnets induce current.

Solenoid

Coiled conductor that intensifies magnetic field around current flow.

Electromagnet

Solenoid with an iron core that greatly strengthens its magnetic field.

Electromagnetic Induction

Generation of electric current in a conductor by a changing magnetic field.

Mutual Induction

Inducing current in a secondary coil via the changing field from a primary coil.

Self-Induction

Induced current within the same coil that opposes the original current change.

Lenz’s Law

Induced current flows in a direction that opposes the change producing it.

Electric Generator

Device converting mechanical energy into electrical energy by induction.

Electric Motor

Device converting electrical energy into mechanical rotation using electromagnetism.

Step-Up Transformer

Transformer that raises voltage and lowers current on the secondary side.

Step-Down Transformer

Transformer that lowers voltage and raises current on the secondary side.

Transformer Law (Voltage)

Vs/Vp = Ns/Np; voltage ratio equals turns ratio (direct relationship).

Transformer Law (Current)

Is/Ip = Np/Ns; current ratio is inverse of turns ratio.

Autotransformer

Single-coil transformer using self-induction to vary voltage (kVp selector).

Primary Circuit

X-ray circuit section with main switch, breakers, autotransformer, timer, primary side of step-up transformer.

Secondary Circuit

Section containing secondary side of step-up transformer, mA meter, rectifiers, and x-ray tube (except filaments).

Filament Circuit

Sub-circuit with rheostat, step-down transformer, and x-ray tube filaments.

mA Meter

Meter in secondary circuit that monitors x-ray tube current.

Rectifier

Solid-state device converting AC to DC for proper x-ray tube operation.

Half-Wave Rectification

Process where only one half of AC waveform reaches the tube; other half blocked.

Full-Wave Rectification

Rectifier arrangement that inverts negative AC half-cycles, producing continuous pulses.

Three-Phase Power

Power using three synchronized AC waveforms; when rectified yields 13–3.5 % ripple.

High-Frequency Generator

Uses high-frequency inversion to produce <1 % ripple DC for x-ray tubes.

Ripple (Voltage)

Percentage variation between maximum and minimum voltage in rectified output.

Line Compensator

Device that automatically adjusts incoming power to the standard 220 V.

Exposure Timer

Circuit component that terminates the exposure after preset time.

Automatic Exposure Control (AEC)

System that ends exposure when detector (ionization chamber) receives adequate radiation.

Ionization Chamber

Radiation detector used in AEC to measure exposure reaching the image receptor.

Filament

Tiny tungsten coil in cathode that emits electrons when heated.

Focusing Cup

Negative metal shroud surrounding filaments that directs electron cloud toward anode.

Kilovolt Peak (kVp)

Peak tube voltage that determines x-ray beam energy and contrast.

Milliampere-seconds (mAs)

Product of tube current (mA) and exposure time; controls x-ray quantity.

Focal Spot

Area on anode where electrons hit; selectable as small or large for resolution vs heat.