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COMEDK2017PhysicsCurrent Electricity

Two resistances are connected in two gaps of a meterbridge. The balance point is 20 ~cm from the zero en(d) A resistance of 15 is connected in series with the smaller of the two. The null point shifts to 40 ~cm . The value of the smaller resistance ( in ) is

Options

  1. A3
  2. B6
  3. C9
  4. D12

Correct answer

C. 9

Step-by-step solution

In first case, at balance point, P Q = l 100-l = 20 100-20 = 1 4 Q=4 P...(i) Let P be the smaller resistance, then in second case at balance point, aligned P+15 Q &= l 100-l^ = 40 60 = 2 3 P+15 4 P &= 2 3 3 P+45 &=8 P P=9 aligned

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