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WorksheetsDc motor
Total questions: 45
Worksheet time: 25mins
WHICH IS MOVING PART IN DC MOTOR
STATOR
ROTOR
YOKE
What type of DC motor is shown?
Short Shunt Cumulative Compound Motor
Short Shunt Differential Compound Motor
Long Shunt Cumulative Compound Motor
Long Shunt Differential Compound Motor
The diagram shows a current-carrying wire placed between two magnetic poles. The current is in the direction shown.
What is the direction of the force on the wire?
towards the bottom of the page
towards the top of the page
towards the left-hand side of the page
towards the right-hand side of the page
A wire XY lies between the poles of a magnet. The diagram shows the upward force on the wire XY caused when there is an electric current in the direction XY as shown.
Three tests are made using this apparatus:
1 The current direction is reversed.
2 The N and S poles are swapped around.
3 The current is switched off.
Which will result in no change in the size of the force on the wire?
1 and 2 only
1 only
2 only
3 only
A coil carries a current in a magnetic field. The coil experiences a turning effect.
Which device uses this effect?
a DC motor
an electromagnet
a relay
a transformer
When the electric current in wire XY is in the direction shown, there is an upward force on the wire.
If the north and south poles of the magnet exchange positions, in which direction will the force on the wire act?
downwards
upwards
to the left
to the right
Which description below best matches the symbol shown?
Control relay coil
Motor starter coil
Contactor coil
Indicating light
How do u obtain desired speed of an armature controlled DC motor ?
by varying armature current
by varying the armature voltage
by varying emf
by varying transformer voltage
Which factors not
affecting the speed of dc motors?
Flux
Current
Applied voltage.
Voltage across the armature
Which of the following amounts of voltage will produce the weakest magnetic field in the electromagnet?
A. 1 A
B. 1.5 A
C. 2 A
D. 2.5 A
Which of the following is not a component of a stepper motor?
A. Windings
B. Rotor and Stator
C. Commutator
D. Brush
E. Both C and D
A pulse can be produce by which means ?
A. Microprocessor
B. Timing Logic
C. Toggle Switch
D. All of the above
How does a Stepper Motor move ?
A. Electrical Pulse
B. Continuous Applied Voltage
C. Alternates from A and B
Servo signal pin must be connected to
any digital pin of Arduino
analog input pins A0 to A5
any one of the PWM pins
5V pin
If servo object is myServo and then servo control signal to make 150 degree angle, is coded as
myServo.write(150);
myServo.Write(852.5);
myServo.write(852.5);
analogWrite(852.5);
How header file is to be defined to code for servo motors?
# define Servo
# include Servo
#include<Servo.h>
Servo myservo;
Speed change of DC motor is controlled by
Enable pin
Input pins
H-bridge
Output pins
to make the Motor A rotate backward and Motor B stop
Pin 9 - GND, Pin 8 - 5V, Pin 7 - GND
Pin 5 - GND, Pin 4 - GND, Pin 3 - GND
Pin 9 - 5V, Pin 8 - GND, Pin 7 - 5V
Pin 5 - GND, Pin 4 - GND, Pin 3 - GND
Pin 9 - 5V, Pin 8 - 5V, Pin 7 - GND
Pin 5 - 5V, Pin 4 - GND, Pin 3 - GND
Pin 9 - GND, Pin 8 - 5V, Pin 7 - 5V
Pin 5 - GND, Pin 4 - GND, Pin 3 - GND
Function of H-Bridge in DC motor control is
Change the speed of the DC motor
Change the direction of the DC motor
Send feedback of the speed of the DC motor
Measures the speed of the DC motor
Which type of current is flowing ?
Alternating current
Direct current
Both
None
What type of current is flowing in the circuit ?
Alternating current
Direct current
Both
None
Which of the following motor has high starting torque?
Slip ring Induction motor
Squirrel cage induction motor
The starting torque of a squirrel-cage induction motor is
Full-load torque
Slightly more than full-load torque
Low
Negligible
Main advantage of an ac motor as compared to a DC motor is
less maintenance
expensive
can work in any environment
controllability
In the image shown, the dark grey shapes are called:
Brushes
Armatures
Commutators
Windings
The part of an electric motor that doesn't spin is called the...
armature
commutator
stator
bearings
Which factors not
affecting the speed of dc motors?
Flux
Current
Applied voltage.
Voltage across the armature
Which of the following amounts of voltage will produce the weakest magnetic field in the electromagnet?
A. 1 A
B. 1.5 A
C. 2 A
D. 2.5 A
Which of the following is not a component of a stepper motor?
A. Windings
B. Rotor and Stator
C. Commutator
D. Brush
E. Both C and D
How does a Stepper Motor move ?
A. Electrical Pulse
B. Continuous Applied Voltage
C. Alternates from A and B
Torque speed characteristic of a series motor is
Parabola
Rectangular Hyperbola
Linear
None
If back e.m.f. suddenly disappears in a d.c. motor
Motor will start as a generator
Motor will stop
Winding will burn due to high armature current
Noting will happen
Speed of d.c. series motor at no load is
1500 rpm
3000 rpm
infinity
zero
For a series motor, field flux is
Proportional to temperature
Constant
Proportional to armature current
Inversely proportional to armature current
No load speed of which of the following motors is high
Shunt motor
Series Motor
Cumulatively Compound Motor
Differentially compound motor
In a four-point starter NVC is connected _______ across the supply.
Series
Parallel
Independently
Series Parallel
Which of the following types of starters are used in DC series motors?
Two-point starters
Five-point starters
three point starter
Four-point starters
What will happen if DC motor is used without starter?
Heavy sparking at brushes
It’ll start smoothly
Will not start at all
Depends on load
A 3- point starter is used to:
Minimize back emf
Minimize armature current
Maximize armature current
Maximize back emf
Which of the following are the disadvantages of a three-point starter?
Field Current Become weak
Disconnect the motor from the supply
The flow of current through the shunt field is decreased.
All of the above
Which of the following are protective devices in DC motor Starter?
No volt coil
Over Load Coil
Both 1 and 2
None
Four-point starter is used when
Motor field current is varied in a narrow range
Motor speed is varied in small range
Motor field current is varied over wide range
Can be used anywhere
A three point starter is considered suitable for
shunt motors
series motors
compound motor
all D.C. motors
By looking at which part of the motor, it can be easily confirmed that a particular motor is D.C. motor?
Frame
Shaft
Commutator
Stator
Which D.C. motor is preferred for elevators
Shunt motor
Series motor
Differential compound motor
Cumulative compound motor
