DC Circuit MCQ Job Interview Exam Higher Study Admission Questions Answers part3

Sunday, 22 December 2013

DC Circuit MCQ Job Interview Exam Higher Study Admission Questions Answers part3
  
  1.   Identical wires of nichrome and copper are connected in series in a circuit. This  results in greater heat in nichrome.
      2.       Two resistance are in parallel and give equivalent resistance of 6/5 Ω. One of the resistances is broken and the effective resistance is 2 Ω. The resistance of the broken resistor is 3 Ω.

      3.       Two identical cells connected in series send 10 A through 5 Ω resistor. When they are connected in parallel, they send 8 A through the same resistor. The terminal resistance of each cell is 2.5 Ω.

Let E and r be the e.m.f and internal resistance of each cell.

For series grouping, 2E =(5+2r)*10…..(1)

For parallel grouping, E=(5+r/2)*8 …..(2)

       Solving eq (1) & (2), r=2.5Ω

     4.       Two batteries of different e.m.fs and same internal resistances are connected in series with an external resistance and current is 3 A. When polarity of one is reversed, the current is 1 A. The ratio of e.m.f s is 2.

     
      5.       n similar resistors each of resistance r when connected in parallel have the total resistance R,
            When these resistances are connected in series, the total resistance is  n^2R.

     
     6.       Kirchhoff’s current law at a junction deals with conservation of charge.

     7.       Kirchhoff’s voltage law deals with conservation of energy.

     8.       A cell supplies a current of 0.9 A through 2 Ω external resistance and 0.3 A through 7 Ω external resistance. The internal resistance of the cell is 0.5 Ω.

Let E and r be the e.m.f,

For the first case       0.9= E/2+r  ,

For the second case 0.3= E/7+r ,

Solving these two equation r= 0.5 Ω



     9.       A 50 V battery is connected across 10 Ω resistor. The current is 4.5 A. The internal resistance of the battery is 1.1 Ω.
  
    10.   An ordinary dry cell can deliver a current of about 1/8 A or 0.125  A.





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