please help me in this question on network ?

Discussion in 'General Electronics Chat' started by munna007, Jun 29, 2011.

  1. munna007

    Thread Starter Active Member

    Jul 23, 2008
    51
    0
    Hello friends....in this questions the answer is (b) option.....this is from indian engg. services exam.

    if we apply mesh in loop which i have shown , then we find that

    I = (10 - 5 )/10 = 0.5 amp


    V=10 - 6 I = 7 volt (right acc. to answer keys)

    and Rth = 2.4 ohm (i have calculated Rth)


    but if we apply Nodal analysis where V is marked then

    acc to that
    (V-10)/6=(V-5)/4
    V= -5

    so we see that both results r not equal....but in answer keys 7 volt is given....
    plz tell me what is the problem in second method of nodal analysis.? is this wrong ?
     
  2. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    2,283
    326
    There are two currents entering the node marked V; their sum must be zero. You have set them equal rather than setting one equal to the negative of the other.

    Let your equation be (V-10)/6 = -(V-5)/4 and you will get V = 7.
     
  3. munna007

    Thread Starter Active Member

    Jul 23, 2008
    51
    0
    thanku so much sir....i understood my mistake....:)
     
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