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A moving-coil galvanometer has its coil of 24 turns and 12 ohms resistance .by how much the number of turns should be increase so that the current-sensitivity of the galvanometer increases by 25%.if in doing so ,the resistance of the coil increases to 20 ohms,what will be the effect on the voltage-sensitivity of the galvanometer?
ans is-turns must be increased from 24 to 30;voltage sensitivity will fall by 25%.

This is the first part of the sum.

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This is the second part of the answer. Original voltage sensitivity(y) y= 24*A*B/12*c = 2AB/c When current sensitivity is increased the turns become 30. Therefore the new voltage is y= 30*A*B/20*c =1.5AB/c Now calculating the percentage of the new voltage sensitivity in respect to the original 1.5/2 *100 ( A, B and c are constant) = 75% Therefore voltage sensitivity falls by 25%
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