CLRS 341 Exam II Objectives Chapters 3, 4 & 6 Bushong 11th edition

Be able to: Label an x-ray tube diagram. Work an inverse square law problem. Identify a circuit wired in series vs in parallel.

Photon

Atom of light

Watt

One ampere of current that flows through an electric potential of one volt

Amplitude

One half the range from crest to valley over which the sine wave varies

Diamagnetic

Nonmagnetic materials that are unaffected when brought into a magnetic field

Frequency

The number of wavelengths that pass a point of observation per second

Ferromagnetic

Material that is strongly attracted by a magnet and that usually can be permanently  magnetized by exposure to a magnetic field

Quantum

An x-ray photon

Tesla (Gauss)

• SI unit of magnetic field intensity.

• An older unit is the gauss (G).

• 1 T=10,000G 

Electrostatics

Study of fixed or stationary electric charge

Solenoid

Helical winding of current-carrying wire that produces a magnetic field along the axis of the  helix

Volt

SI unit of electric potential and potential difference

Electromagnetic induction

The process of making a ferromagnetic object magnetic.

Amperes

SI unit of electric charge: 1A= 1C/s

Lenz’s law

An electric current inducted by a change in a magnetic field always flows in a direction that  opposes the change that created in

Ohm

electrical resistance

Radiopaque

Referring to a tissue or material that absorbs x-rays and appears bright on a radiograph

Hertz

Unit of frequency; the number of cycles or oscillations that occur each second during simple  harmonic motion

Radiolucent

Referring to a tissue or material that transmits x-rays and appears dark on a radiograph

Electrodynamics

Electric charges in motion

Wavelength

Distances between similar points on a sine wave; the length of one cycle

Frequency

Number of cycles or wavelengths of a simple harmonic motion per unit time. Expressed in  Hertz (Hz). 1 Hz = 1 cycle/s

Insulator

Material that inhibits the flow of electrons within a conductor or during heat transfer 

Coulomb

SI unit of electric charge 

Conductor

Material that allows heat of electric current to flow

What is the velocity of all x-rays?

3 x 10^8 m/s 

Describe the wave-particle duality theory

• Both types of photons (visible light & x-ray) exhibit similar behaviors of particles and waves 

• X rays = more like particles than waves.

The relationship between matter and energy is described in what famous equation?

 E=mc^2 

What is the relationship between energy and frequency?

c=fλ

What is the relationship between energy and wavelength?

E=hf

What are characteristics of electromagnetic radiation

• It exist everywhere

• Wide energy range

• Has both electrical and magnetic properties

• No mass

• No electrical charge

What are the three means by which electrification can be created? 

Conduction, friction and induction 

What are the four electrostatic laws? 

1. unlike charges attract  

2. like charges repel  

3. coulombs law of electrostatic force (follows inverse square law)  

4. electric charges are uniformly distributed except at regions of high curvature 

Distinguish between an electrical conductor, insulator, semiconductor & superconductor.

• Conductor: electrons can easily flow (copper, aluminum) 

• Insulator: does not allow electrons to flow (rubber, glass)  

• Semiconductor: under some conditions behaves like an insulator and in others behaves as a conductor (silicon, geranium)  

• Superconductor: electrons flow without resistance (titanium, Niobium) 

Conductor

Electrons can easily flow (copper, aluminum) 

Insulator

Does not allow electrons to flow (rubber, glass)

Semiconductor

Under some conditions behaves like an insulator and in others behaves as a conductor (silicon, geranium)  

Superconductor

Electrons flow without resistance (titanium, Niobium)

Ohm’s Law

V=IR

What is the relationship between current and resistance?

According to Ohm’s Law, the voltage across the entire circuit or any portion of it is equal to the current multiplied by the resistance.

• !!! CHECK !!! Direct relationship

What is magnetic induction? Example? 

• Changing magnetic field induces an electrical current in a circuit 

• !!! NEED EXAMPLE !!!

What is the unit of electric potential? 

Volt

Oersted’s experiment demonstrated what principle? 

Relationship between electricity and magnetism ( any charge in motion induces a magnetic field) 

What is an electromagnet? What is one advantage of an electromagnet? 

• A coil of wire wrapped around a metal core. Creates a temporary magnetic field once electric current flows.

• The one advantage is that it can be turned off.

Faraday’s law states the magnitude of the induced current depends on what four factors?

1. Strength of magnetic field  

2. Velocity of magnetic field as it moves past the conductor  

3. Angle of the conductor to the magnetic field  

4. # of turns in the conductor 

Describe primary role of an electric generator/electric motor.

Convert mechanical energy into electrical energy or electrical energy into mechanical energy.

What is the difference between alternating and direct current? Examples and waveforms. 

• AC: current isn’t constant and moves in different directions (alternators) oscillates 

• DC: varies in intensity and always moves in the same direction (batteries) unidirectional

What type motor powers the rotating anode of an x-ray tube? 

Electromagnetic induction motor

Describe primary role of an electric transformer 

Transforms electric potential and electric current into higher or lower intensity 

Define turns ratio. How is it related to “step up” and “step down” transformers?

• Turns ratio: change in voltage is directly proportional to the ratio of the number of turns of the secondary coil to the number of turns in the primary coil.  

• Step up: ratio > 1

• Step down: ratio < 1 

What are the 3 types of transformers? 

• Closed-core transformer

• Autotransformer

• Shell type transformer 

Describe the general design of an x-ray tube (external & internal structures) 

External structure

• Xray tube supports

  • Ceiling support

  • Floor to ceiling

  • C arm

  • Mobile 

  • Ct

The internal structures of the x-ray tube are the anode and the cathode -- two primary parts of an x-ray. Each of these (the anode and cathode) is an electrode, and any electronic tubes with two electrodes is a diode. Therefore, the x-ray tube is a special kind of diode.

The external structure of the x-ray tube consists of three parts: the support structure, the protective housing, and the glass or metal enclosure

Describe the parts of the anode and the induction motor.

Induction motor consists of:

• Starter (outside glass or metal)

• Rotor (inside glass or metal enclosure)  

The target is the area of the anode that is struck by electrons 

What is the purpose of a dual filament? What material are they made of?

• The two filaments supply separate electron beams to produce two final points

• Made of tungsten

From what/where do the electrons “boil” off?

The filament

Tungsten is the material used for the target in diagnostic radiography. List the 3 main reasons. 

• Atomic number

• Thermal conductivity

• High melting point 

At what point are x-rays made? 

When the electrons hit the target 

X-ray tube failure may result from…

Heat or energy use