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a moving coil galvanometer has resistance 20 ohm show full deflection for current 50mA how will you convert galvanometer to ammeter of range 20A and voltmeter of 120v |
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Answer» Explanation: A moving coil galvanometer has resistance 20 ohm show full deflection for current 50mA how will you convert galvanometer to AMMETER of range 20A and voltmeter of 120v 50 convert galvanometer to ammeter of range 20A Current Range can be extended using Shunt across (S) 50mA = 0.05 A 20 Ω 20 * 0.05 = 1 V Current across Shunt = 20 - 0.05 = 19.95 A 20 * 0.05 = S * 19.95 => S = 1/19.95 => S = 0.05 Ω ( in PARALLEL) convert galvanometer to voltmeter of 120v ( independent of 1ST change) Can be CONVERTED using High Resistance in series High resistance must have a drop of 120 - 1 = 119V when 0.05 A current flows through it 0.05R = 119 => R = 2380 Ω (in series) if We need to convert it to voltmeter of 120v after converting into 20A Then Drop of 120 -1 = 119 V is required at 20A Current Flow 20R = 119 V => R = 5.95 Ω (in series) |
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