Electricity and Electronics: Ch 2

Card Set Information

Electricity and Electronics: Ch 2
2012-03-03 22:52:12
Electrical Units

EMF, Volts, Current, Resistance
Show Answers:

  1. What is a volt?
    The standard of unit of electromotive force (EMF) or potential difference. An accumulation of electrostatic charge, such as an excess or shortage of electrons, always occurs when we have a potential difference between two points or objects.
  2. How can we EMF?
    When we move an electrical conductor through a fixed magnetic field, or when we surround a fixed electrical conductor with a fluctuating magnetic field.
  3. What is an electric dipole?
    A potential difference between two points, called poles, invariably produces an electric field, represented by electric lines of flux. We call such a pair of electric charge poles an electric dipole.
  4. What does voltage represent in a circuit?
    Voltage represents the driving force, or "pressure," that impels charge carriers to move.
  5. How does current flow work?
    If we provide a conducting or semiconducting path between two poles having a potential difference, charge carriers flow in an attempt to equalize the charge between the poles. This current continues for as long as the path remains intact, and as long as a charge difference exsists between the poles.
  6. What is an ampere?
    The standard unit of current which represents one coulomb (6,240,000,000,000,000,000, or 6.24 x 1018) of charge carriers flowing every second past a given point.
  7. What can an ampere do to you?
    A current of a few milliamperes will give you a rude electrical shock. About 50 mA will jolt you severely, and 100 mA can kill you if it flows through your heart.
  8. What does current depend on?
    The amount of current that flows in an electrical curcuit depends on the voltage, and also on the resistance.
  9. What is resistance?
    Resistance quantifies the opposition that a circuit imposes against the flow of electric current. You can compare resistance to the reciprocal of the diameter of a garden hose (where conductance compares to the actual diameter). For metal wire, this analogy works pretty well. Small diameter wire has higher resistance than large diameter wire made of the same metal.
  10. What is an Ohm?
    The standard unit of resistance, symbolized as an upper case greek letter omega.
  11. Describe the relationship between current and resistance?
    The current flow, for a constant voltage, varies in inverse proportion to the resistance. Take the same voltage, as resistance goes up current goes down.
  12. What is a resistor?
    A component that has been deliberately manufactured to exhibit a certain resistance.
  13. What is the relationship betwen voltage and current when encountering resistance?
    In general, the potential difference, (voltage), arises in direct proportion to the current through the resistance.