a very basic doubt about current...

Discussion in 'General Electronics Chat' started by onlyvinod56, Jul 14, 2010.

  1. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    hello,

    I have a very basic doubt about the direction of flow of current.
    help me here.....

    1. What is current?
    2. Is it an electron flow or something else?
    3. For a battery, where does the current starts from...i mean...'+'...or..'-'?
    4. For a small electronic circuits, why a switch is immediately connected after the + supply?
    5. Why it is not preferred for -ve?
    6. What is the difference between actual current and conventional current?



    thankyou.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    For material that should answer your questions 1, 2, & 6 follow the link - http://forum.allaboutcircuits.com/showthread.php?t=32158

    3. External to the battery, current (flow of electrons) goes from the negative terminal to the positive terminal. You can read up on batteries to see how chemical reactions inside the battery move both positive and negative charges internally.

    4. For any circuit switching the voltage supply before the circuit makes sense. With the switch off, no part of the circuit is "live", so it is safe to handle.

    5. If there is a dual voltage supply, the switch arrangement should be the same. Use a double pole switch to open the voltage supply lines before the circuit that uses them.
     
  3. onlyvinod56

    Thread Starter Active Member

    Oct 14, 2008
    362
    1
    thankyou verymuch
     
  4. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    I often use the following example for Ohm's Law:

    Imagine a water pump that was connected to a 1' diameter pipe.

    • The voltage, or Electro-Motive Force (EMF) would be defined as the "push" or force to get the water out of the pipe.
    • The current would be defined as the width of the pipe (in this case it's 1'). The wider the pipe you have, more current will be able to flow through. In electronics, if you choose a wire that's not capable of much current, and if you apply too much current through the wire, it will turn red and burn.
    • Suppose I put a block inside my 1' diameter pipe; the current would be restricted since it was hitting against that block. In other words, it appears to make the pipe a smaller diameter. This is defined as a resistor, which restricts current flow.
     
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