RT10

• Ohm's Law describes the manner in which electric current behaves in an electric circuit
• Ohm's Law states that the current passing through a conductor is directly proportional to the potential difference and inversely proportional to the resistance
• Formula: V = IR (Voltage = Amperes x Ohms)
• Current (Amperes) = Volts divided by Ohms
• Resistance (Ohms) is equal to Volts divided by Amperes
• Voltage (Volts) is the product of resistance and current
• In an electric circuit, the result occurs when the resistance is controlled and the conductor is made into a closed path
• Two types of circuits:

  • Series Circuit
  • Parallel Circuit
• Series Circuit:

  • All circuit elements are connected in a line along the same conductor
  • The amount of current is the same through any component in the circuit
  • Rules for a Series Circuit:

  1. The sum of the potential drops equals the potential rise of the source

  2. The current is the same everywhere in the series circuit

  3. The total resistance of the circuit is equal to the sum of the individual resistances
• Parallel Circuit:

  • Contains elements that are connected at their ends rather than lying in a line along the conductor
  • Rules for a Parallel Circuit:

  1. The potential drops of each branch equals the potential rise of the source

  2. The total current is equal to the sum of all the currents in the branches

  3. The inverse of the total resistance of the circuit is equal to the sum of the inverses of the individual resistances
• One important thing to notice is that the more branches you add to a parallel circuit, the lower the total resistance becomes

  • As the total resistance decreases, the total current increases
  • Plugging too many things into one electrical outlet can create a real fire hazard
• Rules for Parallel Circuit:

  • The sum of the currents through each circuit element is equal to the total circuit current
  • The voltage across each circuit element is the same and is equal to the total circuit voltage
  • The total resistance is inversely proportional to the sum of the reciprocal of each individual resistance
• • Interaction occurs at greater than 10 KeV, interacting with the outermost orbital shell and causing ionization, then losing energy and replacing the lost electron
  • 20% probability
  • Dangerous, especially to the radtech

  3. Photoelectric Effect:

  • Important for creating images in the radiograph
  • 75% probability
  • Greater than or equal to 30 KeV can produce photoelectric effect
  • Interacts with the inside atom, absorbing the atom
  • Produces photoelectron, interacting with the film causing it to black

  4. Pair Production:

  • Used in nuclear medicine
• • Does not happen in x-ray or diagnostic modalities, only in nuclear medicine facilities
  • 1.02 mEv Annihilation Process: when positron and negatron fuse together, producing gamma radiation

  5. Photodisintegration:

  • Interaction occurs at 10 MeV
  • Happens in radiation therapy, bombarding the nucleus causing it to emit nuclear fragments
  • Nuclear fragments can be x-ray, gamma rays, or any radiation
• 1. ray interaction in matter:

  1. Classical Scattering, Reigleigh Scattering, Thompson Scattering:

  • The incident x-ray will interact with the atom but will just skim it, changing direction and causing the atom to vibrate
  • Interaction occurs at less than 10 KeV
  • Only interacts during atomic level
  • Produces scatter radiation
  • 5 to 10% chance or probability
  • No ionization or energy reduction

  2. Compton Scattering:

  • Produces back scatter radiation
• Dr. William Gilbert:

  • Coined the term "electrica," a Latin word describing the static charge that develops when certain materials are rubbed against amber

  Electricity:

  • General term encompassing a variety of phenomena resulting from the presence and flow of electric charge
  • Includes lightning, static electricity, and the flow of electrical current in an electrical wire

  Basic Circuitry:

  • Matter has mass and energy equivalence and may also have electric charges
  • Electrically neutral, meaning the total number of positive charges is equal to the total number of negative charges
• Four Fundamental Properties of Matter:

  1. Mass

  2. Form

  3. Energy Equivalence

  4. Electric Charge

  Units of Electric Charges:

  1. Electrons

  2. Protons
• Electrons are the smallest unit of electric charge with a negative electric charge of 1e = 1.6 x 10^-19 C
• Protons are positively charged particles
• Electrification occurs due to the movement of negative electric charges and can be created in 3 ways:
• Contact: two objects come in contact so that the charges can move from one object to the other, distributing evenly between objects
• Friction: one object is rubbed against another, causing electrons to travel from one to the other
• Induction: charging an object without touching it to any charged object, through the process of electric fields acting on each other without contact
• Earth is a huge reservoir for stray electric charges
• Two studies of electricity are Electrostatic and Electrodynamics
• Electrostatic is the study of stationary electric charges and includes four laws:
• Unlike charges attract, like charges repel
• Coulomb’s Law
• Electric Charge Distribution
• Electric Charge Concentration
• Electrostatic Force is the force of attraction between unlike charges or repulsion between like charges
• Friction can cause a transfer of charge if two materials are rubbed together, with electrons being rubbed off from one material to the other
• Coulomb’s Law states that electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance between them
• Electric Charge Distribution states that electric charge distribution is uniform throughout or on the surface
• Electric Charge Concentration states that electric charges are concentrated along the sharpest curvature, with the electric field being more intense in areas of maximum curvature
• Electrodynamics, also known as electricity, is the study of electricity in motion
• Electric Circuit is an unbroken loop of conductive material that allows electrons to flow continuously
• Ohm's Law describes how electric current behaves in an electric circuit
• Voltage (V) is the potential difference between two points applied across a wire or an electric component
• Current (I) is the rate at which charge is flowing