A microammeter has a resistance of 100W and a full scale range of 50 µA. It can be used as a voltmeter or a higher range ammeter provided a resistance is added to it. Pick the correct range and resistance combination(s).
(1) 10V range with 200 kW resistance in series.
(2) 50V range with 10 kW resistance in series.
(3) 5 mA range with 1W resistance in parallel.
(4) 10 mA range with 1 kW resistance in parallel.

Options

A. 10V range with `200KOmega` resistance in series
B. 50V range with `10kOmega` resistance in series
C. 5mA range with `1kOmega` resistance in parallel
D. 10mA range with `50kOmega` resistance in parallel

Answer

1

Explanation

Given G=`100Omega, lg=50muA`
Consider the case (a)
`V=lg(G+R)` when R is in series
`10=(50xx10^(-6))(100 +R)`
or `R+100=2xx10^(5)`
or `R=200x x10^(3)-100`
or `R=200` kilo ohm approximately
This is the correct range and resistance combination.