A micrometer has a resistance of  $100\Omega$ and a full scale range of  $50\mu A.$  It can be used as a voltmeter or a higher range ammeter provided a resistance is added in series or parallel to it. Pick the correct range and resistance combination(s).

$$\begin{gathered} R_A=100\Omega \\ {I}_{ƒ}=50\times {10}^{-6} \\ \mathbf{\left(}\mathbf{a}\mathbf{\right)}{V}_{\max }=50\times {10}^{-6}[100+10\times {10}^3] \\ V_{\max }\cong 50\times {10}^{-6}\times {10}^4\cong 0.5V \\ \mathbf{\left(}\mathbf{b}\mathbf{\right)}{V}_{\max }=50\times {10}^{-6}[100+200\times {10}^3]\cong 50\times {10}^{-6}\times 200\times {10}^3\cong 10V \\ \mathbf{\left(}\mathbf{c}\mathbf{\right)}50\times {10}^{-6}\times 100=x5\times {10}^{-3} \\ x=10A I_{\max }\cong 10A \\ \left(d\right)50\times {10}^{-6}\times 100=x \\ x=5\times {10}^{-6}\times 100=x{I}_{\max }=55\times {10}^{-6}A \end{gathered}$$