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A galvanometer can be converted into a voltmeter of certain range by connecting a resistance of `880Omega` in series with it. When the resistance of `420Omega` is connected in series, the range becomes half. Find the resistance of galvanometer. |
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Answer» Correct Answer - `40Omega` Let G be the resistance of galvanometer. If a resistance R is connected in series of galvanometer it works as a voltmeter of range 0 to V volt. The current for full scale deflection of a voltmeter is `I_g=(V)/(R+G)` In first case, `I_g=(V)/(880+G)` In second case, `I_g=(V//2)/(420+G)=(V)/(2(420+G))` `:. (V)/(880+G)=(V)/(2(420+G))` or `880+G=840+2G` or `G=40Omega`. |
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