A voltmeter of resistance `1000 Omega` gives full scale deflection when a current of `100 mA` flow through it. The shunt resistance required across it to enable it to be used as an ammter reading `1 A` at full scale deflection is

Options

A. 10000 ohm
B. 9000 ohm
C. 222 ohm
D. 111 ohm

Answer

D

Explanation

As we know
R = 1000 ohm
`C=I_(g)R=100 xx 10^(-3) xx 10^(3)=100V " " …(i)`

`:.` voltage `V=I_(g)((R r)/(R+r)) " " …(ii)`
from (i) & (ii) we get
`100=I_(g)((R r)/(R+r ))`
`100=1xx((1000r)/(1000+r))`
`10^(5)+100r=1000r`
`10^(5)=(1000-100)r`
`10^(5)=900r`
`(100000)/(900)=r`
`r=111Omega`