A microammeter has as resistance of `100 Omega` and full scale range of `50 muA`. It can be used a voltmeter or as ahigher range ammeter provided a resistance is added to it. Pick the correct range and resistance combinations
50 V range with `10 kOmega` resistance in series
b.`10 V` range with `200 kOmega` resistance in series
c. 5mA rangw with `1Omega` resistance in parallel
`10 mA` range with `1Omega` resistance in parallel

Options

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

Explanation

To increase the range of ammeter a parallel resistance (called shunt) is required which is given by

`S=(i_g/(i-i_g))G`
For option ( C), `S=((50 times 10^-6)/(5 times 10^-3-50 times 10^-6)) (100)=1 Omega`
To change it in voltmeter, a high resistance R is put in series, where R is given by `R=V/j_g-G`
For option (B), `R=10/(50 times 10^-6)-100=200 k Omega` Therefore (B) and (C ) are correct