In a ammeter `0.2%` of main current passes through the galvanometer. If resistance of galvanometer is `G`, the resistance of ammeter will be

Options

A. `(1)/(499) G`
B. `(499)/(500) G`
C. `(1)/(500) G`
D. `(500)/(499) G`

Answer

C

Explanation

If S is the resistance of the shunt connected in parallel to the coil of galvanometer, then the same potential difference must be there across shunt and galvanometer coil. 0.2% of total current pass through the galvanometer then 99.8% of current must be passing through the shunt. Equating potential difference across the shunt and the galvanometer coil we get the following:
Assume I to be the main current `(0.002i) xx G = (0.998i) xx S rArr S = G//499`
Resistance of the ammeter is a resultant of G and S, which are connected in parallel to each other.
`(1)/(R ) + (1)/(G) + (1)/(S) =(1)/(G) + (499)/(G) = (500)/(G)`
`rArr R = (G)/(500)` Hence option (c ) is the correct choice.