DC Motors and Generators
Study online at https://quizlet.com/_i20wly
1. What is the purpose of a motor?: The purpose of a motor is to convert electrical energy into
mechanical energy.
2. What is the process of electromagnetic induction?: A rotatable coil of wire with a current
passing through it has a magnetic field. When it is placed in between the poles of a permanent magnet, the two
magnetic fields attract and repel each other to create torque, a turning force on the wire.
3. How is the direction of motion of a motor found?: An easy way to find the direction of motion
in which the loop moves is to apply Flemings left hand rule.
4. What are the rules of Flemings left hand rule?: First finger = magnetic field direction (north
to south).
Middle finger = current.
Thumb = motion of the coil.
5. What is a commutator?: A commutator is a conductive ring in two pieces.
6. How is electrical contact made with a commutator?: Electrical contact is made with a
commutator using small carbon brushes.
7. Where is the maximum torque position in a motor?: The maximum torque is found where
the coil (called the armature) lies parallel with the magnetic field.
8. What is an armature?: Iron cores wrapped with copper wire
9. What is the rotating part of a motor known as?: The rotor.
10. What is the stationary part of a motor known as?: The stator.
11. How is a motor with a high starting torque created?: To create a motor with high starting
torque, an initially high field strength is required.
12. What are the characteristics of the series wound motor?: - All of the input flows through
the field windings.
- A few turns of thick wire is used.
- It allows a high starting current.
- It produces a high starting torque.
- The speed reduces as the mechanical load increases.
13. What are series wound motors used for?: They are used as engine starter motors and for
operation of retractable flaps and slats.
14. What is a disadvantage of a series wound motor?: A disadvantage is that without anything
to slow them down, series wound motors can easily overspeed.
1/3
Study online at https://quizlet.com/_i20wly
1. What is the purpose of a motor?: The purpose of a motor is to convert electrical energy into
mechanical energy.
2. What is the process of electromagnetic induction?: A rotatable coil of wire with a current
passing through it has a magnetic field. When it is placed in between the poles of a permanent magnet, the two
magnetic fields attract and repel each other to create torque, a turning force on the wire.
3. How is the direction of motion of a motor found?: An easy way to find the direction of motion
in which the loop moves is to apply Flemings left hand rule.
4. What are the rules of Flemings left hand rule?: First finger = magnetic field direction (north
to south).
Middle finger = current.
Thumb = motion of the coil.
5. What is a commutator?: A commutator is a conductive ring in two pieces.
6. How is electrical contact made with a commutator?: Electrical contact is made with a
commutator using small carbon brushes.
7. Where is the maximum torque position in a motor?: The maximum torque is found where
the coil (called the armature) lies parallel with the magnetic field.
8. What is an armature?: Iron cores wrapped with copper wire
9. What is the rotating part of a motor known as?: The rotor.
10. What is the stationary part of a motor known as?: The stator.
11. How is a motor with a high starting torque created?: To create a motor with high starting
torque, an initially high field strength is required.
12. What are the characteristics of the series wound motor?: - All of the input flows through
the field windings.
- A few turns of thick wire is used.
- It allows a high starting current.
- It produces a high starting torque.
- The speed reduces as the mechanical load increases.
13. What are series wound motors used for?: They are used as engine starter motors and for
operation of retractable flaps and slats.
14. What is a disadvantage of a series wound motor?: A disadvantage is that without anything
to slow them down, series wound motors can easily overspeed.
1/3
