SSC JE Electrical Engineering 2014 Set 2 Paper

In case of veries–
When motor are connected in series and are in running position, speed ∝ (Voltage)∝ $\left(\frac{\mathit{V}}{2}\right)$ (i) (Since the voltage across each motor = $\frac{\mathit{V}}{2}$ ) and current is ${\mathit{I}}_{\mathit{a}}$ .
${\mathit{N}}_{\mathit{s}}\propto \frac{\mathit{V}}{2\mathit{I}}$ … (i)
In case of parallel– When the motor is connected in parallel and are in running position, speed ∝ (Voltage) (V). (Since voltage across each motor = V) and current is $\frac{\mathit{l}\mathit{a}}{2}$
$\mathit{N}\mathit{p}\propto \frac{2\mathit{V}}{\mathit{d}}$ … (ii)
From both the equation
$\frac{\mathit{N}\mathit{s}}{\mathit{N}\mathit{p}}=\frac{\frac{\mathit{V}}{2\mathit{I}}}{\frac{2\mathit{V}}{\mathit{I}}}$
N parallel = 4 N series.