4Q Physics 2

• Resistors


  An electronic device that opposes the flow of charges
• Ohm's law


  Current flowing through the human body depends on two factors: 1) Voltage applied to the body 2) Resistance of the body
• Electric shock


  The lower the resistance, the greater the shock
• Circuit breakers and fuses


  A safety device that closes a circuit when too much current is in it
• Electrical Measuring devices

  • Analog ohmmeter - resistance
  • Analog ammeter - current
  • Analog voltmeter - voltage
  • Multimeter - current, voltage, resistance, temperature, etc.
  • Analog electric meter - energy
• Electronic circuit


  Composite of wires, voltage sources, resistance, and other electronic components with provision for current
• Resistor color code

  1. 1st band gives 1st number

  2. 2nd band gives 2nd number

  3. 3rd band gives # of zeros

  4. 4th band gives tolerance or ±
• Continuity test

  • Open circuit - indicates high resistance
  • Short circuit - zero ohms of resistance
  • Closed circuit - indicates low resistance
• Ammeters and voltmeters


  Read from left to right : linear scales
• Ohmmeter


  Read from right to left : nonlinear scales
• RC circuit


  Includes capacitor and resistor
• Transient response / time constant


  Time associated with the capacitors ability to charge or discharge within a certain percent of maximum supply voltage
• Magnetism


  Force of attraction or repulsion caused by the movement of charged particles. NOT charged.
• Magnetic pole


  • Regions at each end of a given magnet where the magnetic properties of a magnet are strongest
  • Electric charges can be isolated, magnetic poles cannot
• Magnetic field lines


  Show both the direction and the strength of a bars magnetic field
• Magnetic Field


  • Space around the magnet in which the magnetic force is exerted. Illustrated as parallel paths.
  • Measured in units of Tesla (T)
• Electromagnetic induction


  Inducing voltage by changing the magnetic field around a conductor
• Faradays Law


  The induced voltage in a coil is proportional to the number of loops and multiplied by a magnetic field changes within those loops
• Generators


  Converts mechanical energy into electrical energy
• Transformers


  • Used to step voltages up and down
  • Primary coil - connected to a voltage source
  • Secondary coil - connected to a galvanometer
• Electromagnetic waves


  Composed of vibrating magnetic and electric fields that regenerate each other. Travels by the speed of light (300, 000 km per sec)
• Like poles repel, unlike poles attract
• Turbine


  The wheel captures wind, water, etc in order to produce electrical energy
• Electromagnetic (EM) wave


  Transverse waves without a medium
• Electromagnetic spectrum


  • Radio waves
  • Microwave
  • Infrared
  • Visible light
  • Ultraviolet
  • X-ray
  • Gamma ray
• Radio waves


  • Longest wavelength and lowest frequency. Converts radio waves into sound waves.
  • GPS / global positioning system - measure the time it takes a radio wave to travel from satellite to the receiver
  • MRI / magnetic resonance imaging - uses short radio wave with a magnet to create an image
• Microwave


  • Shortest wavelength and highest frequency of radio waves
  • RADAR / Radio detection and ranging - used to find the speed on an object by sending out radio waves and measuring the time it takes them to return
• Infrared


  • Shorter wavelength and higher frequency than microwave
  • Heat waves - warm object that give off heat energy than cool objects
  • Thermogram - a picture that shows regions of different temperatures in the body
• Visible light


  • Red light - longest wavelength
  • Violet light - shortest wavelength
• Ultraviolet


  • Carry more energy than visible light
  • Sterilize - used to kill Bacteria
  • Ultraviolet rays - too much can cause skin cancer
  • Sun rays - causes your skin to produce Vitamin
• X-ray


  • Carry a great amount of energy and can penetrate most matter
  • Laser rays - used to check for tiny cracks in structures
• Gamma ray


  Used in radiation treatment to kill cancer cells
• All electromagnetic waves travel at 300,000,000 m/sec
• Long wavelength = lowest frequency, short wavelength = highest frequency, the higher the frequency the higher the energy
• People give off infrared rays, heat lamps give off infrared waves
• ROYGBIV - red, orange, yellow, green, blue, indigo, violet
• Bones and teeth absorb x-ray
• Incredible Hulk is a victim of gamma radiation
• Luminous object


  One that produces light
• Illuminated object


  One that reflects light