A separately excited $$DC$$ shunt motor is driving a fan load whose torque is proportional to the square of the speed. When $$100$$ $$V$$ are applied to the motor, the current taken by the motor is $$8$$ $$A,$$ with the speed being $$500$$ $$rpm.$$ At what applied voltage does the speed reach $$750$$ $$rpm$$ and then what is the current drawn by the armature? Assume the armature circuit resistance to be $$1\,\,\,\Omega .$$ Neglect brush drop and mechanical losses.

A $$DC$$ shunt generator delivers $$60$$ $$KW$$ at $$240$$ $$V$$ and $$360$$ $$rpm.$$ The armature and field resistances are $$0.015\,\,\,\Omega $$ and $$60\,\,\,\Omega $$ respectively. Calculate the speed of the machine running as a shunt motor and taking $$60$$ $$KW$$ input at $$240$$ $$V.$$ Allow $$1$$ volt per brush for contact drop.

A $$5$$ $$kW,$$ $$200V$$ $$d.c.$$ shunt motor has an armature resistance of $$1$$ $$ohm$$ and shunt field resistance of $$100$$ $$ohms.$$ At no-load, the motor draws $$6A$$ from a $$200$$ $$V$$ supply and runs at $$1000$$ $$rpm.$$ The rotational loss of the machine is ______________ $$W$$ and the no load torque is ____________ $$N$$-$$m$$

The field coil of a two-pole $$d.c.$$ series motor is made up of two identical sections In one case
$$(i)$$ of two sections of the field coil are connected in series, and in another case
$$(ii)$$ the two sections are connected in parallel. If the motor takes the rated current in both the cases, then ratio of torque $$(1):$$ torque $$(2)$$ and speed $$(1):$$ speed $$(2)$$ respectively are