Term1fundamentals

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juliav
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217232
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Term1fundamentals
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2013-05-02 11:22:05
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fundamentals
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Term 1 Fundamentals
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  1. What is an Isolation Transformer?
    A transformer that has its secondary winding physically and electrically isolated from the primary winding.
  2. What is the transformer?
    A magnetic device that changes the voltage, current, and impedence without changing the frequency.
  3. What are the common transfomer efficiencies?
    90% to 99% full load.
  4. Define power factor.
    What is the calculation?
    • Ratio of real power to apparent power.
    • Watts/VA
  5. In what form is energy of a capacitor stored\?
    electrostatic field
  6. In what form is energy of a inductor stored?
    electromagnetic field
  7. What is a dielectric?
    Insulating material.
  8. Define Inductive Reactance
    The current limiting property of an inductor in an AC circuit.
  9. Define Capactive Reactance
    The current limiting property of a capacitor in an AC circuit
  10. State Kirchhoff's Current Law
    The sum of the currents entering and leaving a point must equal zero.
  11. State Kirchhoff's Voltage Law
    The sum of the voltage drops and voltage sources in a closed circuit must equal zero.
  12. Name three factors that determine the amount of induced voltage in a coil.
    • number of turns of wire
    • strength of the magnetic field (flux density)
    • speed of the cutting action
  13. What is frequency?
    The number of complete cycles per second.
  14. List 3 factors that determine the capacitance of a capacitor.
    • Surface area of the plates
    • Distance between the plates
    • Strength of the dielectric
  15. Explain the current and voltage relationships from phase to line in a wye and delta.
    • wye: Line voltage = root3 * phase voltage
    • delta: Line current = root3 * phase current
  16. What is the equation for power in a 3-phase load?
    • Line: P = root3*V*I
    • Phase: P= 3*V*I
  17. What is a Coulomb?
    quantity measure of electrons. 6.25*10^18
  18. Define Ampere
    rate of electron flow. C/s
  19. Define Voltage
    Electric Potential. The force that pushes electrons through a wire. J/C
  20. define Ohm
    Resistance to current flow (V/A)
  21. Define Watt
    Amount of power being used by a circuit. Energy change must occur to produce watts. J/s
  22. How can the polarity of an electromagnet be determined if the direction of current flow is known?
    Left hand rule. Thumb in the direction of the north pole. Fingers in the direction of current flow
  23. Define Flux Density
    magnetic flux lines per square inch. strength of the magnetic field.
  24. Define Saturation
    when the magnet's strength is increased only slightly with an increase of current.
  25. Define Residual Magnetism
    The amount of magnetism left in a material after the current has stopped
  26. What range of electric current generally causes death and how?
    50-200mA. Fibrillation of the heart.
  27. What is a ground fault?
    An unintended current path to ground.
  28. Define Ohm's Law
    Mathematical relationship between voltage, current, and resistance V=IR
  29. What determines the polarity of magnetism when current flows through a conductor?
    Direction of current flow.
  30. What determines the strength of the magnetic field when current flows through a conductor?
    Amount of current.
  31. What is a vector?
    A line that indicates both magnitude and direction.

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