EE-2 (3)

The sole purpose of a commutator in a dc generator is to

• increase output voltage

• reduce sparking at brushes

• provide smoother output

• convert the induced ac into dc

The shaft torque in a DC motor is less than the total armature torque because of _____in the motor

• copper losss

• field loss

• iron and friction losses

• rotational

The induced emf of armature conductors of a dc motor is

• sinusoidal

• trapezoidal

• rectangular

• none of the above

A dc motor can be looked upon as dc generator with the power flow

• reduced

• reversed

• increased

• modified

The commercial efficiency of a shunt generator is maximum when its variable loss equals ______ loss

• constant

• iron

• friction and windage

• none of the above

The yoke of a DC machine is made up of _______

• Silicon steel

• soft iron

• aluminium

• cast steel

The relationship between generated emf and applied voltage in case of dc generator is given as

• Eg = V + IaRa

• Eg = V – IaRa

• Eg = V

• none of these

In a d.c generator, the generated e.m.f is directly proportional to the ____________

• field current

• pole flux

• number of armature parallel paths

• number of dummy coils

The series field of a short-shunt d.c generator is excited by ____________ currents.

• shunt

• armature

• load 

• external

The open circuit characteristics of a dc generator is the curve between

• V and Ia

• E and Ia

• E0 and If

• none of the above