Question

A microameter has a resistance of `100 omega` and a full scale range of ` 50 muA`. It can be used as a voltmeter or as a higher range ammeter provides a resistance is added to it . Pick the correct range and resistance combination(s)
A. 50 V range with `10kOmega` resistance in series
B. `10V` range with `200kOmega` resistance in series
C. `5mA` range with `1Omega` resistance in parallel
D. 10 mA range with `1Omega` resistance in parallel

Answer 1

Correct Answer - B::C
To increases the range of ammeter a parallel resistance (called shunt) is requried which is given by
`S=((i_(g))/(i-i_(g)))G` for option (c)
`S=((50xx10^(-6))/(5xx10^(-3)-50xx10^(-6)))(100)=1Omega`
To change it into voltmeter, a high resistance `R` is put in series where R is given by `R=(V)/(i_(g))-G`
For option (b) `R=(10)/(50xx10^(-6))-100=200kOmega`