DC Generators And DC Motors – Questions With
Solutions (Ultimate Guide)
DC generator Right Ans - machine that converts mechanical energy into
electrical energy ( DC voltage and current) by using the principle of magnetic
induction
The ends of the wire loop have been connected to two slip rings mounted on
the shaft, while brushes are used to carry the current from the loop to the
outside of the circuit. True or false Right Ans - True
Principle operation of generator Right Ans - Whenever a conductor is
moved within a magnetic field in such a way that the conductor cuts across
magnetic lines of flux, voltage is generated in the conductor.
The amount of voltage generated depends on Right Ans - -The strength of
the magnetic field
-the angle at which the conductor cuts the magnetic field
- the speed at which the conductor is moved
-the length of the conductor within the magnetic field
The simplest elementary generator that can be built is an ac generator. True
or false Right Ans - true
what does elementary generator consists of Right Ans - wire loop mounted
on the shaft, so that it can be rotated in a stationary magnetic field, this will
produce an induced emf in the loop. then sliding contacts (brushes) connect
the loop to an external circuit load in order to pick up or use the induced emf
The pole pieces ( marked N and S ) provide the magnetic field. The pole pieces
are shaped and positioned as shown to concentrate the magnetic field as far
away as possible to the wire loop Right Ans - false, as close as possible
Armature Right Ans - The loop of wire that rotates through the field.
Slip rings Right Ans - The ends of the armature loop are connected to slip
rings, they rotate with the armature
,brushes Right Ans - usually made of carbon, with wires attached to them,
ride against the rings. the generated voltage appears across these brushes
Since DC generators must produce DC current instead of AC current, a device
must be used to change the AC voltage produced in the armature winding into
DC voltage. Right Ans - The commutator
The commutator is constructed from? Right Ans - copper ring split into
segments with insulating material between the segments
Brushes riding against the commutator segments carry the power through
where? Right Ans - Carry the power to the outside circuit
whats the main difference between dc and ac generator construction Right
Ans - DC replaces the slip rings of the ac with a commutator
the commutator mechanically reverses the armature loop connections to the
external circuit. True or false Right Ans - True
The armature has an shaft, and the commutator is attached to the shaft. True
or false Right Ans - True
what does the plates attached to the shaft at the armature provide? Right
Ans - Provide the two connections for the coil of the electromagnet
commutation process Right Ans - The contacts of the commutator are
attached to the shaft of the electromagnet, so they spin with the magnet.
The brushes are just two pieces of springy metal or carbon that make contact
with the contacts of the commutator.
Through this process the commutator changes the generated ac voltage to a
pulsating dc voltage which also known as commutation process.
When the loop is parallel to the magnetic line of flux and no voltage is induced
in the loop, True or false Right Ans - true
Neutral plane Right Ans - Brushes make contact with both of the
commutator segments at this time.
, As the loop rotates, conductors begin to cut through the magnetic line of flux.
Conductor cutting through the south magnetic field is connected to what?
and the north magnetic field is connected to what? Right Ans - South
magnetic field is connected to positive brush and north magnetic field is
connected to the negative brush
the voltage is induced into the loop when Right Ans - the loop is cutting
lines of flux
After 90 degree of rotation, the voltage reaches its neutral point. True or false
Right Ans - false, its most positive point
As the loop continues to rotate, the voltage decreases to zero.
After 180 of rotation, the conductors are again parallel to the lines of flux, and
no voltage is induced in the loop. True or false Right Ans - true
Note that the brushes again make contact with both segments of the
commutator at the time when there is no induced voltage in the conductors
How to increase the amount of output voltage in the generator? Right Ans -
we need to increase the number of turns of wire for each loop.
If a loop contains 20 turns of wire, the induced voltage will be 20 times
greater than that for a single-loop conductor.
loop contains 20 turns of wire and each loop has an induced voltage of 2v,
whats the total voltage? Right Ans - 40V
2V X 20 Loops= 40 V
whats the difference in construction between practical DC generators from
elementary generators Right Ans - generators use electromagnetic poles
instead of the permanent magnets used in our elementary generator
the main advantages of using electromagnetic poles are Right Ans -
increased field strength and possible to control the srength of the fields. by
varying the input voltage, the field strength is varied. by varying the field
strength, the output voltage of the generator can be controlled
major parts of a DC generators are Right Ans - field frame (yoke), rotating
armature, brush assembly
Solutions (Ultimate Guide)
DC generator Right Ans - machine that converts mechanical energy into
electrical energy ( DC voltage and current) by using the principle of magnetic
induction
The ends of the wire loop have been connected to two slip rings mounted on
the shaft, while brushes are used to carry the current from the loop to the
outside of the circuit. True or false Right Ans - True
Principle operation of generator Right Ans - Whenever a conductor is
moved within a magnetic field in such a way that the conductor cuts across
magnetic lines of flux, voltage is generated in the conductor.
The amount of voltage generated depends on Right Ans - -The strength of
the magnetic field
-the angle at which the conductor cuts the magnetic field
- the speed at which the conductor is moved
-the length of the conductor within the magnetic field
The simplest elementary generator that can be built is an ac generator. True
or false Right Ans - true
what does elementary generator consists of Right Ans - wire loop mounted
on the shaft, so that it can be rotated in a stationary magnetic field, this will
produce an induced emf in the loop. then sliding contacts (brushes) connect
the loop to an external circuit load in order to pick up or use the induced emf
The pole pieces ( marked N and S ) provide the magnetic field. The pole pieces
are shaped and positioned as shown to concentrate the magnetic field as far
away as possible to the wire loop Right Ans - false, as close as possible
Armature Right Ans - The loop of wire that rotates through the field.
Slip rings Right Ans - The ends of the armature loop are connected to slip
rings, they rotate with the armature
,brushes Right Ans - usually made of carbon, with wires attached to them,
ride against the rings. the generated voltage appears across these brushes
Since DC generators must produce DC current instead of AC current, a device
must be used to change the AC voltage produced in the armature winding into
DC voltage. Right Ans - The commutator
The commutator is constructed from? Right Ans - copper ring split into
segments with insulating material between the segments
Brushes riding against the commutator segments carry the power through
where? Right Ans - Carry the power to the outside circuit
whats the main difference between dc and ac generator construction Right
Ans - DC replaces the slip rings of the ac with a commutator
the commutator mechanically reverses the armature loop connections to the
external circuit. True or false Right Ans - True
The armature has an shaft, and the commutator is attached to the shaft. True
or false Right Ans - True
what does the plates attached to the shaft at the armature provide? Right
Ans - Provide the two connections for the coil of the electromagnet
commutation process Right Ans - The contacts of the commutator are
attached to the shaft of the electromagnet, so they spin with the magnet.
The brushes are just two pieces of springy metal or carbon that make contact
with the contacts of the commutator.
Through this process the commutator changes the generated ac voltage to a
pulsating dc voltage which also known as commutation process.
When the loop is parallel to the magnetic line of flux and no voltage is induced
in the loop, True or false Right Ans - true
Neutral plane Right Ans - Brushes make contact with both of the
commutator segments at this time.
, As the loop rotates, conductors begin to cut through the magnetic line of flux.
Conductor cutting through the south magnetic field is connected to what?
and the north magnetic field is connected to what? Right Ans - South
magnetic field is connected to positive brush and north magnetic field is
connected to the negative brush
the voltage is induced into the loop when Right Ans - the loop is cutting
lines of flux
After 90 degree of rotation, the voltage reaches its neutral point. True or false
Right Ans - false, its most positive point
As the loop continues to rotate, the voltage decreases to zero.
After 180 of rotation, the conductors are again parallel to the lines of flux, and
no voltage is induced in the loop. True or false Right Ans - true
Note that the brushes again make contact with both segments of the
commutator at the time when there is no induced voltage in the conductors
How to increase the amount of output voltage in the generator? Right Ans -
we need to increase the number of turns of wire for each loop.
If a loop contains 20 turns of wire, the induced voltage will be 20 times
greater than that for a single-loop conductor.
loop contains 20 turns of wire and each loop has an induced voltage of 2v,
whats the total voltage? Right Ans - 40V
2V X 20 Loops= 40 V
whats the difference in construction between practical DC generators from
elementary generators Right Ans - generators use electromagnetic poles
instead of the permanent magnets used in our elementary generator
the main advantages of using electromagnetic poles are Right Ans -
increased field strength and possible to control the srength of the fields. by
varying the input voltage, the field strength is varied. by varying the field
strength, the output voltage of the generator can be controlled
major parts of a DC generators are Right Ans - field frame (yoke), rotating
armature, brush assembly
