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MHT CET Medical202626 April 2026Morning ShiftPhysicsCurrent ElectricityActual

A galvanometer can be converted into a voltmeter of certain range by connecting a resistance of 990 in series with it. When the resistance of 480 is connected in series, the range is halved. The resistance of the galvanometer is

Options

  1. A20
  2. B30
  3. C40
  4. D50

Correct answer

B. 30

Step-by-step solution

Let the resistance of the galvanometer be G and the full-scale deflection current be I_g . When a resistance of 990 is connected in series, the range of the voltmeter is V . V = I_g (G + 990) When a resistance of 480 is connected in series, the range is halved, i.e., V 2 . V 2 = I_g (G + 480) Dividing the first equation by the second equation: V V 2 = I_g (G + 990) I_g (G + 480) 2 = G + 990 G + 480 2(G + 480) = G + 990 2G + 960 = G + 990 G = 30 Answer: 30

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