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15 May 2011 13:00:56 IST

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a glalvanometer with coil resistance of 100 ohms gives a full scale deflection when a current of 1 m

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a glalvanometer with coil resistance of 100 ohms gives a full scale deflection when a current of 1 mA is passed through it. The resistance of the shunt needed to convert this galvanometer into ammeter of range 10 A IS NEARLY EQUAL T0..

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GOPAKUMAR

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Joined: 18 Mar 2010

Posts: 270

15 May 2011 19:54:00 IST

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0.010001 ohm

saharsha kumar keshkar

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Joined: 7 Aug 2008

Posts: 1104

15 May 2011 20:16:12 IST

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Let resistance of galvanometer = R_g and it gives full-scale deflection when current I_g is passed through it. Then,
V_g = I_gR_g -------(i)
Let a shunt of resistance (R_s) is connected in parallel to galvanometer. If total current through the circuit is I.

Then current through shunt:
I_s = (I-I_g)
potential difference across the shunt:
V_s= I_sR_s
or V_s = (I – I_g)R_s -------(ii)
But
V_s=V_g (I - I_g)R_s = I_gR_g

........ .............

so now putting values

Rs=(1mA/(10-1mA))*100ohm = .01 ohms

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