SSC JE Electrical Engineering 2017 Set 4 Paper

DC shunt motor is constant flux motor
${\mathit{E}}_{\mathit{b}}=\mathit{V}\mathit{–}{\mathit{I}}_{\mathit{a}}{\mathit{R}}_{\mathit{a}}$
${\mathit{E}}_{\mathit{b}}=\mathit{k}\mathit{\omega }\mathit{\varphi }$
$\mathrm{k}\mathit{\omega }\mathit{\varphi }=\mathit{V}-{\mathit{I}}_{\mathit{a}}{\mathit{R}}_{\mathit{a}}$
$\mathit{\omega }=\frac{\mathit{v}}{\mathit{K}\mathit{\varphi }}-\frac{{\mathit{I}}_{\mathit{a}}\mathit{R}}{\mathit{K}\mathit{\varphi }}$
So if load is increased then armature current ‘${\mathit{I}}_{\mathit{a}}’$ icre increased, Supply voltage and constant flux speed of the DC shunt motor decrease slightly.