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A potentiometer wire has length of 5 ~m and resistance of 16 . The driving cell has an e.m.f. of 5 ~V and an internal resistance of 4 . When the two cells of e.m.f.s 1.3 ~V and 1.1 ~V are connected so as to assist each other and then oppose each other, the balancing lengths are respectively

Options

  1. A3 ~m , 0.25 ~m
  2. B0.25 ~m , 3 ~m
  3. C2.5 ~m , 0.3 ~m
  4. D0.3 ~m , 2.5 ~m

Correct answer

A. 3 ~m , 0.25 ~m

Step-by-step solution

aligned & K= E R (R+r) L & E =5 ~V , r =4 , L =5 ~m , R =16 & K = 5 16 (16+4) 5 & K =0.8 ~V / m & aligned When ' E₁ ' and ' E₂ ' are connected so as to assist each other array ll & E ₁+ E ₂= K l₁ & 1.3+1.1=0.8 l₁ & l₁=3 ~m array When ' E₁ ' and ' E₂ ' are connected so as to oppose each other, aligned & E ₁- E ₂= K ₂ & 1.3-1.1=0.8 l₂ & l₂=0.25 ~m aligned

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