Electricity, Magnetism, and Electromagnetism

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Electricity, Magnetism, and Electromagnetism

• Bushong Ch. 5
• RTEC 244

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Objectives

• Review of Plancks Equation (B, Ch. 4)
• Electrostatics
• Electricity
• Ohms Law
• Series Parallel Circuits

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Particle Model Quantum Theory

• X-ray is identified among all EM energy by their
  energy.
• Measured in electron volts (eV)
• X-ray 10 keV to 50 MeV
• Wavelength 10 -10 to 10 -14 m
• Frequency 10 18 to 1022 Hz

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E hf Plancks Equation

• E phonton enerty
• h Plancks constant
• f frequency
• How are energy of a photon and frequency related?

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Electrification

• Electrons are often free to travel from one
  valence shell to another.
• An object is electrified it is has too few or too
  many electrons.

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Atom construction

• Because of electron binding energy, valence e-
  often are free to travel from the outermost shell
  of one atom to another.
• What do we know about e- binding energy of an
  atom?

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ELECTRIFICAITON OF OBJECTS

• FRICTION
• CONTACT
• INDUCTION

ELECTRIFICATION BY CONTACT ELECTRONS LEAVE YOUR
BODY CONTACT THE BALLOON
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Electrification

• Electrification process of electrons being
  added or subtracted from an object
• Balloon rubbed against your head (Friction)
  Collects electrons from you - sticks to the wall
  that has a positive charge
• Shuffling across wool rug e on shoes
• Touch door handle es want to escape (Contact)
• Induction electrical fields acting upon each
  other like in the circuitry of the x-ray
  equipment

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Generator - convert mechanical energy to
electrical energy

• THAT CREATE AN ALTERNATING CURRENT ARE CALLED
• AN ALTERNATOR
• CONVERT MECHANICAL ENERGY INTO ELECTRICITY
• EX PORTABLE GAS, ENGINE - GENERATOR

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The Earth

• A huge reservoir of stray electric charges
  electric ground

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Smallest unit of electric charge

• Electron
• Electric charge is the coulomb

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Laws of Electrostatics

• Unlike charges attract like charges repel
• Coulombs law The force is directly proportional
  to the product of the charges and inversely
  proportional to the square of the distance.

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Electrostatic Laws

• Electric charge distribution is uniform
  throughout or on the surface.
• Electric charges of a conductor is concentrated
  along the sharpest curvature of the surface.
• Pg. 74

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Electric Potential

• Energy ?
• Electric charges have potential energy, when
  positioned close to each other.

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ELECTRIC POTENTIAL (EMF)

• MEASURED IN VOLTS
• Potential difference between two charges that
  makes the current flow ( there does not have to
  be an actual flow just the potential difference
  
• The force or strength of electron flow
• 220 volts sent to x-ray machines
• Joule is the SI unit for both mechanical energy
  and work

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VOLT THE POTIENTAL DIFFERENCE

• VOLTMETER MEASURES THE VOLTAGE ACROSS THE CIRCUIT
• AMMETER MEASURES CURRENT
• OHMMETER- MEASURES RESISTANCE OF ONE RESISTOR IN
  CIRCUIT
• SWITCH MUST BE CLOSED FOR CURRENT TO FLOW

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How the current gets to the TUBEInsulated cables
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X-ray imaging system

• Convert electric energy to electromagnet energy.
• A well controlled electrical current is applied
  and converted to mostly heat and a few x-rays.

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Electrodynamics study of electric charges in
motion

• Conductor electrons flow easily
• Insulator electrons do not flow
• Semiconductors some conditions behaves as an
  insulator and others a conductor.

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Electric Circuits

• Modifying electric flow and controlling
  electricity results in an electric circuit.

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CURRENT

• RATE OF ELECTRON FLOW
• AMPERE OR AMP
• 1 AMP 1 COULOMB FLOWING IN 1 SEC
• AC 60 CYCLES PER SEC
• (50 IN EUROPE)

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CURRENT (mA)

• The of electrons flowing past a given point per
  unit of time.
• AC Alternating current when electrons flow in
  one direction and then the other
• DC when electrons all flow in one direction

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• AC E FLOW ALTERNATELY
• DC E FLOW IN ONE DIRECTION
• P 82

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Capacitors

• A device that is capable of accumulating and
  storing an electrical charge

A parallel plate capacitor
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High Voltage Generator- transformers
rectifiers

• High Voltage
• Increases the output voltage from autotransformer
  to the kvp

• Falling Load
• Type of generator used in capacitor discharge
• Voltage falls approx 1 kvp/mas
• operates at shortest time highest mA
• uses series of steps (mA t) to achieve mAs
• Where are these used?

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generators

• Function to change _______energy in to
  ___________energy
• What components are included in the high voltage
  generation or generator
• Electrical current flowing through a conductor in
  one direction is _______
• A battery is a source of direct current

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• WHAT MEASURES ELECTRIC POTIENTAL VOLT
• CURRENT AMP
• ELECTRIC CIRCUIT IS THE PATHWAY FOR ELECTRIC
  CURRENT

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Resistance (OHM)

• The amount of opposition to flow
• Conductor material that permits electrons to
  flow easily
• Insulator - inhibits the flow of electrons

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OHMS LAW V IR

• V POTIENTAL
• A AMPS (CURRENT)
• R RESISTANCE (OHMS)

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OHMS LAW

• V Potential difference in volts
• I Current in amperes
• R Resistance in ohms (?)
• V IR I V/R RV/I

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V IR

• The voltage across the total circuit or any
  portion of the circuit is equal to the current
  times the resistance.
• According to Ohms Law, what would the voltage be
  if the resistance is 2 ? and the current is 4
  ampere?
• A. 2 volt
• B. 4 volt
• C. 8 volt
• D. 10 volt

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V IR

• The voltage across the total circuit or any
  portion of the circuit is equal to the current
  times the resistance.
• According to Ohms Law, what would the voltage be
  if the resistance is 2 ? and the current is 4
  ampere?
• A. 2 volt
• B. 4 volt
• C. 8 volt
• D. 10 volt

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R V/I

• The resistance in a circuit is equal to the
  voltage divided by the current
• According to Ohms Law, what would the resistance
  be if the voltage is 110 volt and the current is
  5 ampere?
• A. 22 ?
• B. 55 ?
• C. 220 ?
• D. 550 ?

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R V/I

• The resistance in a circuit is equal to the
  voltage divided by the current
• According to Ohms Law, what would the resistance
  be if the voltage is 110 volt and the current is
  5 ampere?
• A. 22 ?
• B. 55 ?
• C. 220 ?
• D. 550 ?

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I V/R

• The current across a circuit is equal to the
  voltage divided by the resistance.
• According to Ohms Law, what would the current be
  if the voltage is 12 volt and the resistance is
  1.5 ??
• A. 2 Ampere
• B. 4 Ampere
• C. 6 Ampere
• D. 8 Ampere

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I V/R

• The current across a circuit is equal to the
  voltage divided by the resistance.
• According to Ohms Law, what would the current be
  if the voltage is 12 volt and the resistance is
  1.5 ??
• A. 2 Ampere
• B. 4 Ampere
• C. 6 Ampere
• D. 8 Ampere

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Electric current

• Electricity the flow of electrons along a
  conductor.
• E- travel along a conductor in two ways.
• Alternating current (AC) - sine wave
• Direct current (DC)
• X-ray imaging systems require 20 to 150 kW of
  electric power.
• Circuit symbols and functions. Pg. 80

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X-ray Tubes have complicated wiring

• SERIES CIRCUIT (all circuit elements are
  connected in a line along the same conductor )
• PARALLEL CIRCUIT (elements bridge the circuit
  rather than lie in a line along the conductor)

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Simple SERIES Circuit
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PARALLEL SERIES circuit

• EX CHRISTMAS LIGHTS
• One line all bulbs go out
• Separate lines
• Only bulb burns out

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Series Circuit Rules

• Current IT I1 I2 I3
• Voltage VT V1 V2 V3
• Resistance
• RT R1 R2 R3

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Parallel Circuit Rules

• Current
• IT I1 I2 I3
• Voltage
• VT V1 V2 V3
• Resistance
• 1 1 1 1
• RT R1 R2 R3
• (REMEMBER TO FLIP SIDES RT/1

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Set up the formulas

• What is the total current in a series circuit
  with 3 resistances, each supplied with 10
  amperes?
• What is the total voltage in a series circuit
  with 3 resistances, each supplied with 10 volts?
• What is the total resistance of a series circuit
  with resistances of 2.5?, 4.2?, 6.8??

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Answers

• 4. 10 amperes
• 5. 30 volts
• 6. 2.5?, 4.2?, 6.8? 13.5

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Set up the formulas

• What is the total current in a parallel circuit
  with 3 resistances, each supplied with 10
  amperes?
• What is the total voltage in a parallel circuit
  with 3 resistances, each supplied with 10 volts?
• What is the total resistance of a parallel
  circuit with resistances of 2.5?, 4.2?, 6.8??

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Answers

• 7. 30 amperes
• 8. 10 volts
• 9. 1/2.5?, 1/4.2?, 1/ 6.8?
• 0 .4 .24 0.14 1/.78 1.28 ?