99.  A moving coil galvanometer of resistance 20 Ω gives a full scale deflection when a  current of 1 mA is passed through it.  It is to be converted into an  ammeter reading 20 A on full  scale deflection.  If shunt wire of 0.005 Ω only is available then what resistance should be connected in series with the galvanometer coil.
1 .     99 . 955 Ω 2 .     79 . 995 Ω 3 .     59 . 295 Ω 4 .     19 . 955   Ω

Dear student,A moving coil galvanometer can be converted by connected a small resistance called shunt in parallel to the Galvanometer.S=IgGI-IgS=10-3×2020-10-3=0.001ohmSo shunt resistance of 0.001ohm will be used.But we have only 0.005ohm so to produce effective resistance of 0.001ohm let we add R ohm in series with galvanometer,10.001=120+R+10.005R=19.99Ohm19.95ohmRegards

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