RAT Physics Exam 4

What is an image in radiation therapy?

An x-ray to verify isocenter, An x-ray to verify a treatment portal, A CT for simulation—tumor localization

Types of Electrical Material

Conductors
Insulators
Semiconductors
Superconductors

What type of material do electrons move freely?

Conductor

What is a superconductor?

A conductor that has zero resistance to low temperatures and currents that will flow continuously once started

Examples of Conductors

Copper
Silver

What is Electric Power?

The rate at which electrical energy is used to do work

How is Electrical Power measured?

Watts

How is 1 Watt produced?

By one ampere of current flowing with an electrical pressure of one volt

What material sends electrons in one direction?

Semiconductors

Examples of Semiconductors

Silicon

What material can produce magnetic fields in MRI machines?

Superconductors

What material do electrons flow easily?

Conductor

Characteristics of Insulator

Electrons are fixed
No current can flow

Examples of Insulator

Wood
Plastic
Glass

What is Electrodynamics?

The study of electric charges in motion

When does an Electrical Potential Energy Difference occur?

when one end of a conductor has excess to electrons while the other end has a deficiency of electrons

What happens to the electrons when an Electrical Potential Energy Difference occurs?

electrons will move from an area of excess to an area of deficiency which causes an electric current or flow.

What is an electric current?

flow of electrons over a set amount of time that is measured in amperes or milliamperes

What is the unit of measure for current?

Amperes (amps)

What is an Ampere?

One coulomb of electric charge flowing per second

What is the unit of measure for Electric Charge?

Coulomb

What is Direct Current?

Flow of electrons in a conductor that flow in one direction

What is milliamperage?

the measurement of the QUANTITY or the number of electrons passing from cathode to anode per second.

A milliampere is what fraction of an ampere?

1/1000 of an ampere

Electrons flow from ____ to ____

negative cathode to positive anode

What is voltage?

Electrical pressure or electromotive force applied to the electrons in the conductor

What is resistance?

The opposition of current flow

What is resistance measured in?

Ohms (Ω)

What is Ohm's Law?

The relationship between voltage, current, and resistance in a circuit.

Explain the unit of current in Diagnostic radiographic equipment

It uses a variety of milliamperes (mA) to regulate the number of electrons needed to produce x-ray photons (50-800 mA)

What is the direction of electron flow in an X-Ray Tube?

Electrons flow from the negative cathode to the positive anode.

What gives electrons higher energy?

Higher voltages

When voltage increases, what happens to the current?

It increases

What is alternating current?

A type of current where charges flow half the time in one direction and the other half of the time in the other direction (Used in home electricity)

What is the standard Alternating Current frequency in the United States?

60 cycle per second

One cycle per second is referred to as:

1 Hertz (Hz)

What is Power?

the rate at which energy is used

What is power measured in?

Watts (W)

What is Electromagnetic Induction?

the principle of electrons moving through a conductor and creating a magnetic field around the conductor

What is Potential Difference?

Electrons flow in response to the difference in pressure

What is another term for Volts?

Electromotive Force

What is electromotive force?

the maximum potential difference between two points on a circuit

The force with which electrons can be described is:

potential difference
electromotive force
voltage (V)

In a x-ray tube, what is the rotating anode driven by?

By the rotor that's attached to an induction motor

What is Body Habitus?

build, physique, and general shape of the human body

The induction motor operates based on what principle?

mutual induction

What are the components of an Induction Motor?

rotor and stator

What determines the amount of resistance in a circuit?

Conductive material
Length of conductor
Cross sectional diameter
Temperature

How will the length of conductor determine the amount of resistance in a circuit?

as length increases, so does resistance

Temperature Resistance

as heat builds, electrons collide with one another-more resistance

What happens in ohm's law, when one factor is changed?

it effects all remaining factors

Current flow is demonstrated by:

Sinusoidal or sine waveforms

Cross Sectional Diameter

as wire diameter doubles, resistance is halved

In direct currents, electrons will flow until?

Until the electricity is turned off

What is a fundamental property of Electric Currents?

The magnetic field around the conductor

How is an electromagnet made?

when a coiled conductor becomes magnetized and its magnetic field lines interact with the electric field in the coil

What do Radiographic equipment utilize?

electromagnet current to produce electric current

What is Electromagnetic Induction?

The relationship between current, a ferromagnetic core, and a changing magnetic field

What does a changing magnetic field induce?

an electric field

The four factors that regulate the strength of induced current are:

-Strength of the magnetic field
-Speed of the motion between field lines and the conductor
-The angle between the magnetic field lines and the conductor
(90 degree angles will produce the most amount of voltage)
The number of turns in a conducting coil

What angle between magnetic field lines and the conductor produce the most amount of voltage?

90 degree angles

What will more turns in a conducting coil create?

More voltage

What converts mechanical energy to electrical energy?

electric generator

What converts electrical energy to mechanical energy?

electric motor

What is Electrical Energy?

the energy carried by moving electrons in an electric conductor.

What is Mechanical Energy?

the energy that is possessed by an object due to its motion or due to its position.

What energy cannot be seen, but one of the most useful forms of energy?

Electrical Energy

What is Electricity?

When electrons are forced along a path in a conducting substance such as a wire

Forms of mechanical energy

kinetic energy and potential energy

What is a Rotor?

Center of induction motor that is rigidly connected to the target through the anode stem

What is a stator?

An electric motor with an even number of electromagnets placed around the rotor than turns the rotor at very high speed causing the target to rapidly rotate during x-ray production.

What is kinetic energy?

energy of motion

What is potential energy?

stored energy of position

What is the anode stem made of?

Molybdenum

What is the rotor made of in the induction motor?

Copper and iron bars

What is the Z Number of Molybdenum?

42

What temporarily stores electric charges?

Capacitors

Where do capacitors store energy?

Portable X-ray machines

What is used in x-ray circuits to produce high energy x-rays?

Voltages of 20,000 to 120,000 V

1 kilovolt (kV) = _____ volts (10^3 v)

1000 volts

What type of energy is used for Diagnostic X-Ray?

Kilo-voltage (kV)

What energy makes the patient absorb more of the X-ray?

kV Diagnostic X-ray

In radiation therapy, we treat using:

Mega voltage (mV - 10^6)

What type of energy has more exit dose?

mV

Automatic Exposure Control (AEC)

Device that terminates the exposure when a specific quantity of radiation has reached the image receptor (IR).

Kilovoltage peak (kVp)

The maximum or peak voltage that is used during an x-ray exposure (Quality)

Digitally Reconstructed Radiograph (DRR)

Localization film produced from 3D CT data into a 2D film

the cathode in the xray tube head is

negative

Thermeonic Emission

boiling off of the electrons from a heated surface

X-ray tube target made out of:

Tungsten

What is the Z number of Tungsten?

74

What is the spinning of the anode for?

Heat dissipation

electromagnetic spectrum

the range of wavelengths or frequencies over which electromagnetic radiation extends.

Electron binding energy

the amount of energy needed to remove the electron from the atom

nuclear binding energy

the amount of energy necessary to break up a nucleus into its component nucleons

Isotopes are

atoms of the same number of protons with different number of neutrons

Isobars are

The same number of protons and neutrons

Isotones are

the same number of neutrons

Isomers are

molecules that have the same molecular formula but different structures

4 forces of nature strongest to weakest

strong,electromagnetic, weak, gravitational