Help on this please

Discussion in 'Homework Help' started by ecjohnny, Jul 16, 2005.

  1. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
    142
    0
    This is the only question i dont know in my homework.. anyone able to give me the solution/working on this please.

    Question: Write out the voltage in the two loops.( i think is something to do with Maxwell's loop method that i have learnt in that chapter)

    [​IMG]
     
  2. liketesla

    New Member

    Jul 16, 2005
    3
    0
    Try these steps:

    First redraw the circuit and change the direction of I2 to clockwise. I find that it makes circuit analysis because it becomes more systematic.

    Second, appy KVL around both loops to find a system of two equations in two unknowns. I found the following two eqs.

    6*i1 - 12 + 3 + 3(i1 - i2) = 0

    3(i2 - i1) - 3 + 16i2 = 0

    After solving these two equations for i1 and i2, I found i2=.333 amps, and i1=1.111.

    but remember that i2 must be negated because it was originally drawn in the opposite direction.

    so the final answer is i1=1.11 amps, and i2 = -.333 amps
     
  3. liketesla

    New Member

    Jul 16, 2005
    3
    0
    Whoops, forgot the rest of it.

    I think most people would assume the bottom node to be ground, so that is what I did. So using Ohms law, the node between the 12v source and 6 ohm resister is
    -6.66 v. That would make the top node = 5.34 v. Then if we travel down the center branch, the voltage source causes the center node to be reduced by 3 volts, resulting the that node voltage = 2.34 v.

    Hope that makes sense.
     
  4. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
    142
    0
    Thanks. joejester and liketelsa.
    sorry..One more question here :

    A parallel-plate capacitor has a capacitance of 300pF. it has 9 plates, each
    40mm x 30mm, separated by mica having a relative permittive of 5. Calculate the thinkness of the mica.

    The answer is (1.416mm).

    The answer is given but i just cant get the working right. Can someone nice work this out for me???
     
  5. ecjohnny

    Thread Starter Senior Member

    Jul 16, 2005
    142
    0
    its in my book. The answer in the book might be wrong anyway.
     
  6. liketesla

    New Member

    Jul 16, 2005
    3
    0
    Which book are you working from and what is the problem number?
     
Loading...