Voltage in Electrical Systems

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Voltage in Electrical Systems
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Objectives

• Differentiate between AC and DC current
• Identify the most common source of DC voltage
• Describe the sequence for connecting a DC circuit
  in series so that the voltages will add
• Identify 4 components of a circuit, including a
  source, conductor, control element, and load
  (light bulb), also give their symbols

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Parts of a General Electric System

• Voltage source batteries or generators
• Control element examples switch, volume
  control, variable-speed control on a drill
• Conductors any material that permits the
  movement of electrical energy usually wire
• Electrical load common users of electricity
  examples motors, heaters and lights
• Electrical circuit a closed path connecting
  voltage sources, control elements and electrical
  loads which allows current to flow

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Two Types of Electricity

• Direct current (DC) electric charge in wires
  moves in one direction produced by batteries
• Alternating current (AC) electric charge moves
  back and forth in the wire many times a second
  produced by alternators or generators

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Volts
Voltage the prime mover that causes electrical
charge to move in all electrical systems Volts
the unit of measure for voltage
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Batteries
AC or DC depends on the voltage source used
The most common source of DC voltage is the
battery A battery is made up of two or more
cells
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Different kinds of batteries
Dry-cell battery contain a paste material
which serves as an electrolyte, a carbon rod
which serves as an electrode. These cause a
chemical reaction to produce voltage Wet-cell
battery contains a liquid electrolyte (usually
acid) and lead electrodes
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Cells

• Primary cells cannot be easily recharged
• Secondary cells - can be easily recharged

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• Electrodes terminal or post on batteries
• Cathode the negative electrode
• Anode the positive electrode
• Voltages add in series VTV1V2

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From Fig 1-35 Four shorthand symbols for
components in a circuit

• The battery
• The light bulb
• The switch
• The conductors -

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• Connecting a series circuit
• Connecting a parallel circuit

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Summary.

• How do you differentiate between AC and DC
  current?
• What is the most common source of DC voltage?
• How do you connect a DC circuit in series so that
  the voltages will add?
• How would you draw the symbols for the components
  of a circuit, including a source, conductor and
  load (light bulb)?

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Objectives

• Describe how frequency and hertz relate to AC
  current
• Briefly describe how voltage can be considered a
  forcelike quantity
• Name at least three types of voltmeters

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Objectives (contd)

• 4. Practice color coding resistors

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Important Facts
The main source of AC electricity electrical
power-generating plants Frequency The rate of
change of alternating voltage Hertz The unit
of measure for frequency Voltage acts like a
force Electron carries the fundamental unit of
electrical charge negatively charged particle in
the atom
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• Two kinds of electrical charge
• Positive charge
• Negative charge -

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What is an ATOM? An atom is the origin of
electrical charge. Unlike charges attract Like
charges repel. Electrical forces create a voltage
whenever the positive and negative charges are
separated.
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Three common ways of creating a voltage
difference

• Chemical Chemical energy in dry or wet cells
  separates the charge to form a positive pole and
  a negative pole.
• Magnetic/Mechanical A coil of wire moving in a
  magnetic field produces a force on electrical
  charges that separates the positive and negative
  charges.
• Light Light energy that falls on certain
  materials causes the separation of electrons from
  their atoms.

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• Four types of voltage-measuring devices
• Voltmeter A Voltage measuring device
• Digital multimeters (DMM) the part of this meter
  that measures voltage is called a DVM.
• Oscilloscope
• Conventional or analog volt-ohm-milliammeter

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• Resistor a device used to slow down the flow of
  electrons
• Diode A device to change AC current to DC
  Current. It allows the electricity to flow in
  only one direction.
• Capacitor Stores electrons. Soaks up
  electrons for use later.

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• 120 ? - 5
• 120 X .05 6
• 120 6 126
• 120 6 114
• Tolerance range 126 114
• If the resistor reads within this range on a
  meter, it is a good resistor.

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Soldering Tips

• Plug up the iron and let it get extremely hot.
• Clean the tip by wiping it, as you turn it, on a
  wet sponge.
• Touch your piece of solder to the tip in order to
  melt some solder on the tip. This is called
  TINNING the tip.

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Soldering Tips (contd)

• 4. Touch the hot iron to the circuit board to
  heat the board
• 5. Without removing the iron from the board,
  touch the length of solder to the heated board.
  It will melt like butter.
• 6. Remove the solder wire, then the iron.

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Soldering Tips (contd)

• 7. A good solder looks like a Hersheys Kiss
• 8. Keep your tip clean by wiping it on the wet
  sponge occasionally
• 9. Trim back excess wire from the component

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Soldering Safety

• Remain alert at all times. Never goof off
• Serious burns may result!
• Soldering irons are extremely hot. Keep
  electrical cords away from them.
• If you get burned
• Run under cold water or put burn in ice
• Tell the teacher immediately

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Soldering Safety (contd)

• Never apply lotion to a burn. Lotion can hold
  heat in causing a more severe burn.
• Never point a soldering iron at anyone for any
  reason
• Always replace iron on soldering iron stand when
  not in use