Concept:A galvanometer is converted into a voltmeter by connecting a high resistance in series with it.Explanation:The total voltage measured is related to the galvanometer current by:V=Ig(R+r)where V=40 V, Ig=20 mA=0.02 A, and r=10Ω.Rearrange to find the series resistance R:R=IgV−rR=0.0240−10R=2000−10=1990ΩAnswer:The required value of R is 1990Ω, so the correct option is B.
