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A galvanometer, having a resistance of 50 , gives a full scale deflection for a current of 0.05 A. The length in metre of a resistance wire of area of cross-section 2.97 10⁻² ~cm ^2 that can be used to convert the galvanometer into an ammeter which can read a maximum of 5 A current is : (Specific resistance of the wire .=5 10⁻⁷ - m )

Options

  1. A9
  2. B6
  3. C3
  4. D1.5

Correct answer

C. 3

Step-by-step solution

Resistance of galvanometer, G=50 Full scale current, i_g=0.05A=2.97 10⁻² ~cm ^2=2.97 10⁻² 10⁻⁴ ~m ^2=2.97 10⁻⁶ ~m ^2i=5 ~A =5 10⁻⁷ - m Required resistance to convert the galvanometer into ammeter, R= i_g G i-i_g = 0.05 50 5-0.05 = 25 4.95 l A = 50 99 l= 50 99 A = 50 99 2.97 10⁻⁶ 5 10⁻⁷ = 50 99 29.7 5 =10 0.3=3 ~m

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