The full-scale deflection current of an ammeter is 1 mA and its internal resistance is 100 Ohm. This is to have full deflection when 100 V…

Given that, full scale deflection of ammeter (Im) = 1 mA

Internal resistance (Rm) = 100 ohms

Voltage (Vm) = 1 × 10-3 × 100 = 0.1 V

Required full deflection (V) = 100 V

Series resistance $({R_{se}} = {R_m}\left( {\frac{V}{{{V_m}}} - 1} \right) = 100\left( {\frac{{100}}{{0.1}} - 1\;} \right) = 99.99\;k{\rm{\Omega }})$