Help me help a friend. Ohm's Law, series, parallel resistors

Discussion in 'Homework Help' started by Leanna, Apr 24, 2015.

  1. Leanna

    Thread Starter New Member

    Apr 24, 2015
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    0
    My friend doesn't understand this and I want to help. I know it sounds dumb, I'm really good at math I just didn't know what the symbols mean. Thanks for anyone nice enough to help :)
     
  2. ericgibbs

    Senior Member

    Jan 29, 2010
    2,499
    380
    hi,
    The 'power' label is usually the product of the Voltage and Current in the circuit, the 'R's are the values of the resistors in the circuits.
    The tables along side the circuits give these values.
    E
     
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  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    This is a test covering the application of Ohm's Law, series, parallel, and series-parallel resistors. It it the first thing an electronics student should learn.
    Ω is resistance in Ohms
    R in the diagram means "Resistor" -the diagrams are meant to represent circuits.
    A is the amps flowing through the indicated resistor. The more common symbol is "I",
    W is the quantity of watts dissipated by the resistor. The more common symbol is "P".
    V is the voltage across the resistor. The more common symbol is "E"

    See the OHm's Law Triangle about 1/3 the way down on the right side of this page:
    https://en.wikipedia.org/wiki/Ohm's_law

    Series and parallel circuits are discussed at the link below:
    https://en.wikipedia.org/wiki/Series_and_parallel_circuits
     
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  4. WBahn

    Moderator

    Mar 31, 2012
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    4,788
    If your friend doesn't understand what the symbols mean, then they aren't ready to take this test at all and they need to take a step back and make sure they have a handle on the fundamentals.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,415
    3,354
    Power is usually calculated using any one of three formulas:

    W = I x V
    W = I x I x R
    W = V x V /R

    You can derive any one formula from another by applying Ohm's Law, I = V/R

    In the diagram supplied, Power means something else. In this case Power refers to the excitation voltage required to produce the desired result.
    If you look at Problem 1 on the left. The Total V = 132V. This is the value of Power applied to the circuit.

    BTW, your answers for Problem 1 are incorrect.

    Also the sheet is badly labelled. Totals do not mean that one should arithmetically ADD the values in the column. Look at Problem 7 on the right. The value for Totals is lower than R1. How is that possible?

    An understand on series and parallel circuits is essential.
     
    Last edited: Apr 24, 2015
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