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Homework Help: Magnitude and direction of the current in conductor

  1. Jan 15, 2009 #1
    I have a few questions on three circuits problems that I have already solved. I explained how I arrived at my answers and included diagrams. I would appreciate any help in confirming that my answers are correct. Thank you!

    1. The diagram below shows electric currents in conductors that meet at junction P.

    http://www.stmary.ws/physics/home/marys_java/regents/Januar14.gif [Broken]

    What are the magnitude and direction of the current in conductor PQ? (1) 9 A toward P (2) 9 A toward Q (3) 5 A toward P (4) 5 A toward Q

    I chose choice #4, 5 A toward Q because when 3 and 4 are added you get 7. But, because of the 2 moving in the opposite direction, it takes away from the overall total of 7 leaving you with 5.

    2. Which diagram below correctly shows currents traveling near junction P in an electric circuit?

    http://www.stmary.ws/physics/home/marys_java/regents/June0114.gif [Broken]

    (1) 1 (2) 2 (3) 3 (4) 4

    I chose choice #4 because that is the only one where all the arrows correctly show that that the current is traveling near junction P. The arrows indicate the direction of the current toward the junction.

    3. Determine the following using the figure below:
    http://img509.imageshack.us/img509/8186/circuitoh0.png [Broken]

    R(total)= 25 ohms
    I(total)= 4 amps
    V(x-->y)= 20 volts
    V(y-->z)= 20 volts
    V(x-->z)= 40 volts
    I(5 ohm resistor)= 1.3 amps
    Power(10 ohm resistor - not the parallel ones)= 160 watts
    Power (15 ohm parallel resistors)=26.7 watts

    I included my answers as well as how I broke down the complex circuit into a simple circuit so I could arrive at those answers using the V=IR formula and working backwards.
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 15, 2009 #2
  4. Jan 15, 2009 #3
  5. Jan 15, 2009 #4
    The answers looks correct to me!
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