# DC Motor: Principle, Construction, Working, Applications of DC Motor

Definition

The device which converts the electrical energy into mechanical energy is called a motor. The electric motor which is operated by Direct Current (DC) is called a DC motor.

##### Principle of DC Motor

When a current-carrying conductor is placed in a magnetic field, it experiences a torque as well as tends to rotate. This torque is given by

τ = NIBA cos α

Simply put, when an electromagnetic field, as well as an electrical field, interacts, mechanical pressure is created. The DC motor works with that principle. This is known as motoring action. The direction of this force is given by Fleming’s left-hand rule and also its magnitude is given by F = BIL. Where, B = magnetic flux density, I = current well as L = length of the conductor within the magnetic field.

##### Construction of DC Motor
###### Rotor

Blades originate from the “rotate” implying it is the electric rotating part of a dc motor. It dynamically rotates when the voltage is applied to the armature winding. This will certainly create a mechanical activity for a dc motor. The rotor is made from:

• Shaft
• Armature core
• Brush
• Commutator
• Armature windings

###### Brush

Brushes are affixed to the commutator as a bridge to deliver the electrical power from the supply circuit to the rotor. Brushes are typically made from Carbon or Graphite material.

###### Commutator

The commutator is the type of a split ring. The ring is made from copper and split in two or even more depending upon the number of armature windings.

The split section is attached to the armature winding. The major purpose of the commutator is to provide the electric current to the armature windings.

###### Poles

Poles in the stator are made use of to stimulate a particular series of magnetic poles to make certain the rotor is rotating. It is separated right into Post Core as well as Pole Shoes.

###### Armature

These are a number of coils wound on an iron cylinder.

Permanent Magnets

These provide a magnetic field to an armature.

##### Working of DC Motor

The rotor is generally present within the motor, while the stator is located on the outside. The rotor consists of coil windings that are powered by the DC current (battery/ electrical source) as well as the stator contains either permanent magnets or electromagnetic windings.

When the motor is powered by DC current, a magnetic field is produced within the stator, bring in and driving away from the magnets on the rotor. This triggers the rotor to start rotating. To maintain the rotor turning, the motor has a commutator.

When the rotor straightens with the magnetic field, it would certainly stop spinning, yet in this situation, the commutator would turn around the current with the stator and in this manner turn around the electromagnetic field. In this manner, the rotor can keep rotating.

##### Back EMF in Motors

According to fundamental laws of nature, no energy conversion is possible up until there is something to oppose the conversion. In the case of generators, this opposition is provided by magnetic drag, but in the case of dc motors, there is back emf.

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When the armature of a motor is turning, the conductors are also reducing the magnetic flux lines, and also thus according to Faraday’s law of electromagnetic induction, an emf causes in the armature conductors. The direction of this induced emf is such that it opposes the armature current (Ia).

##### Removal of Jerks in Armature

As a result of using a commutator, a little problem happens that the torque vanishes each time the current changes its direction. This produces the jerks in smooth operating of the armature.

So, by utilizing the number of coils wound on a soft iron core, the jerks can be avoided and consistent and steady torque is produced.

• Good performance
• Relatively high torque density
• DC motor runs smoothly
• Speed regulation range is wide
• Low electromagnetic interference
• Sliding contact between commutators and brush produces sparks
• Mechanical problems
• High maintenance
• Reliability issues
##### Applications of DC Motor
• Used in conveyors, turntables
• Used to empower hydraulic pumps due to varying speed of motors
• Remote control cars, trains, other toys use dc motors
• DC motors due to their durability and efficiency are used in electric cars.

### MCQs

• What is the principle behind the operation of a DC motor?
• A) Ohm’s Law
• B) Coulomb’s Law
• C) Faraday’s Law of Electromagnetic Induction
• D) Fleming’s left-hand rule
• Answer: D) Fleming’s left-hand rule
• Which component of a DC motor dynamically rotates when voltage is applied to the armature winding?
• A) Brush
• B) Commutator
• C) Rotor
• D) Stator
• What material are brushes typically made of in a DC motor?
• A) Copper
• B) Aluminum
• C) Graphite or Carbon
• D) Steel
• Answer: C) Graphite or Carbon
• What is the main purpose of the commutator in a DC motor?
• A) To provide electrical power to the rotor
• B) To connect the motor to the power source
• C) To regulate the speed of the motor
• D) To control the direction of rotation
• Answer: A) To provide electrical power to the rotor
• What component in the stator of a DC motor is used to stimulate a specific sequence of magnetic poles?
• A) Brushes
• B) Commutator
• C) Poles
• D) Armature
• In a DC motor, what causes the rotor to start rotating?
• A) Application of mechanical force
• B) Interaction of magnetic fields
• C) Thermal expansion
• D) Electrical resistance
• Answer: B) Interaction of magnetic fields
• What phenomenon opposes the armature current in a DC motor?
• A) Back EMF
• B) Lenz’s Law
• C) Coulomb’s Law
• How are jerks in the armature of a DC motor prevented?
• A) By increasing the current flow
• B) By decreasing the number of coils
• C) By using a soft iron core
• D) By increasing the commutator size
• Answer: C) By using a soft iron core
• What is an advantage of a DC motor?
• A) Low torque density
• B) Limited speed regulation range
• C) Relatively high torque density
• D) High electromagnetic interference
• Answer: C) Relatively high torque density
• Which of the following is a disadvantage of a DC motor?
• A) Smooth operation
• B) Low maintenance
• C) Sliding contact between commutators and brushes produces sparks
• D) Low reliability
• Answer: C) Sliding contact between commutators and brushes produces sparks
• What are DC motors commonly used for?
• A) Heating systems
• B) Sound systems
• C) Conveyor belts and turntables
• D) Water purification
• Answer: C) Conveyor belts and turntables
• What type of motor is typically used in remote control cars and toys?
• A) AC motor
• B) DC motor
• C) Induction motor
• D) Synchronous motor
• What is the principle governing the removal of jerks in the armature of a DC motor?
• A) Lenz’s Law
• C) Ohm’s Law
• D) Use of soft iron core
• Answer: D) Use of soft iron core
• Which law describes the induced emf in the armature conductors of a rotating DC motor?
• A) Ampere’s Law
• C) Gauss’s Law
• D) Newton’s Third Law
• What range of speed regulation do DC motors typically offer?
• A) Narrow
• B) Wide
• C) Moderate
• D) Variable
• What is the main purpose of brushes in a DC motor?
• A) To generate magnetic fields
• B) To regulate current flow
• C) To provide electrical connection to the rotor
• D) To control the direction of rotation
• Answer: C) To provide electrical connection to the rotor
• What application often utilizes DC motors due to their durability and efficiency?
• A) Solar panels
• B) Air conditioning units
• C) Electric cars
• D) Water pumps
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### FAQs (Frequently Asked Questions) Related to DC Motor Tutorial:

1. What is a DC motor and how does it differ from other types of motors?
• A DC motor is an electric motor that operates on direct current (DC), converting electrical energy into mechanical energy. Unlike AC motors, which run on alternating current, DC motors provide continuous and controlled motion in one direction.
2. What is the principle behind the operation of a DC motor?
• The principle behind a DC motor’s operation is based on the interaction between magnetic fields and current-carrying conductors. When a current-carrying conductor is placed in a magnetic field, it experiences a force that causes it to rotate, as described by Fleming’s left-hand rule.
3. What are the main components of a DC motor and their functions?
• The main components of a DC motor include the rotor (which rotates when voltage is applied), brushes (which deliver electrical power to the rotor), commutator (which reverses the current direction to maintain rotation), poles (which stimulate magnetic fields), and armature (coils wound on an iron cylinder).
4. How does a DC motor work?
• A DC motor works by applying DC current to the rotor, creating a magnetic field within the stator. This magnetic field interacts with the rotor’s magnets or windings, causing it to rotate. The commutator ensures that the rotor continues to spin by reversing the current direction as needed.
5. What is back EMF in DC motors and how does it affect their operation?
• Back EMF, according to Faraday’s law, is an induced electromotive force that opposes the armature current in a turning DC motor. It plays a crucial role in regulating the motor’s speed and preventing excessive current flow.
6. How are jerks in the armature of a DC motor prevented?
• Jerks in the armature of a DC motor are prevented by using a soft iron core and multiple coils wound around it. This setup ensures a consistent and steady torque output, avoiding fluctuations in motion.
• Advantages include good performance, relatively high torque density, smooth operation, wide speed regulation range, and low electromagnetic interference. Disadvantages include sparking due to sliding contact between commutators and brushes, mechanical problems, high maintenance, and reliability issues.
8. Where are DC motors commonly used?
• DC motors find applications in conveyors, turntables, hydraulic pumps, remote control cars, trains, toys, and electric cars due to their durability and efficiency.
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### Summary: DC Motor Tutorial

The DC Motor tutorial offers a comprehensive overview of the principles, construction, working, advantages, disadvantages, and applications of DC motors. Here’s a brief summary:

1. Definition: A DC motor is an electrical device that converts electrical energy into mechanical energy using direct current (DC).
2. Principle of DC Motor: DC motors operate based on the interaction between magnetic fields and current-carrying conductors, producing mechanical motion known as motoring action.
3. Construction: A DC motor consists of essential components such as the rotor, brush, commutator, poles, and armature, each playing a crucial role in its operation.
4. Working: DC motors work by applying DC current to the rotor, creating a magnetic field that interacts with the stator to produce rotational motion.
5. Back EMF in Motors: Back electromotive force (EMF) opposes the armature current in DC motors, playing a vital role in regulating speed and preventing excessive current flow.
6. Removal of Jerks in Armature: Jerks in the armature are prevented by utilizing soft iron cores and multiple coils to ensure consistent torque output.
7. Advantages: DC motors offer good performance, relatively high torque density, smooth operation, wide speed regulation range, and low electromagnetic interference.
8. Disadvantages: Challenges include sparking due to sliding contact between commutators and brushes, mechanical issues, high maintenance, and reliability concerns.
9. Applications: DC motors find applications in conveyors, turntables, hydraulic pumps, remote-controlled vehicles, toys, and electric cars due to their durability and efficiency.

This tutorial provides a comprehensive understanding of DC motors, from their fundamental principles to practical applications, offering valuable insights for both beginners and enthusiasts in the field of electrical engineering.