At $$50\% $$ of full load, the armature current drawn by a $$d.c.$$ shunt motor is $$40$$ A when connected to a $$200$$ $$V$$ $$d.c.$$ mains. By decreasing the field flux, its speed is raised by $$20\% $$ this also causes a $$10\% $$ increase in load torque. Calculate the percentage change in field current. The armature resistance including the brushes is $$1$$ $$Ohm.$$ Neglect saturation and armature reaction.

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

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 ____________ $$N$$-$$m$$

A $$200V$$, $$10$$ $$kW$$ lap-wound $$d.c.$$ generator has $$10$$ poles and $$500$$ conductors on it's armature. If the pole face covers $$80\% $$ of the pole pitch, the pole face conductors required to fully compensate for armature reaction will be ___________________ conductors/pole.