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Electric Motor
1.0Master Electro-Mechanical Conversion in Minutes
Learn how a current-carrying wire behaves inside a magnetic field. Master the core working principle of a DC motor, understand the structural role of split-ring commutators, and apply Fleming's Left-Hand Rule to determine rotational direction easily—all formatted in clean, plain text for simple copy-pasting.
2.0Learning Outcomes
After completing this lesson, you will be able to:
- State the fundamental working principle of an electric motor.
- Use Fleming's Left-Hand Rule to find the direction of force on a current-carrying conductor.
- Identify the primary components of a DC motor (armature, commutator, brushes) and explain their specific functions.
- Describe the step-by-step mechanical working of a motor over a full rotation cycle.
- List the structural features that distinguish commercial electric motors from simpler school-lab models.
3.0Introduction
An electric motor is a device that powers various electronic machines, such as fans, washing machines, etc, by conversion of energy from one form to another. In the case of an electric motor, electric energy is converted into mechanical energy. In simple words, it can be said that the electric motor is a device used to move things via electricity making it an essential element of various everyday use appliances.
4.0Principle Of An Electric Motor
Electric motors operate on the principle of electromagnetic induction, a process in which a current-carrying conductor placed in the magnetic field experiences a force. This is the force that pushes the conductor to move, resulting in the conversion of electrical energy to mechanical motion.
To understand it more clearly, imagine a horseshoe magnet and place a current-carrying rectangular coil in between the poles of the magnet. Open the circuit, and the coil carrying the current will start moving under the influence of the current and magnetic field produced by the magnetic. Analyse the following electric motor diagram:
The current carrying coil doesn’t move in any direction; rather, it follows the flemings’ left-hand rule to determine its direction. According to this rule, When you hold your left hand with all three fingers perpendicular to each other, you will know the direction of the conductor. In the Flemings’ left-hand rule:
- Thumb: It represents the direction of motion or force in which the object is moving.
- Index finger: It represents the direction of the magnetic field from north to south.
- Middle finger: It shows the direction of the electric current in the conductor (positive to negative terminal)
5.0Main Components of an Electric Motor
An electric motor is made up of various components, which include:
- Stator: The part of the motor which is stationary; it has a magnetic field produced by permanent magnets or electromagnets.
- Rotor: The moving part of the motor that reacts to the magnetic field to cause movement.
- Commutator (in DC motors): A device which reverses the direction of the flow of the current in the coil, hence, the rotor would continue to move in the same direction.
- Brushes (in DC motors): Conductive materials that make contact with the commutator to supply current to the rotor.
- Armature: The coil of wire attached to the rotor, which carries the current and produces the magnetic field.
- Shaft: A rotating part that transfers mechanical energy to the load (e.g., a fan blade or a wheel).
6.0Electric Motor Winding
Motor winding is the process of wrapping copper wire coils around the stator or rotor of an electric motor. These windings play a critical role in developing the magnetic field required for the motor to operate. A winding carries the electrical current, which serves to generate the magnetic field that interacts with other parts of the motor to produce motion or mechanical energy. Electric Motor winding affects the efficiency and performance of the motor, which in turn depends on:
- The number of turns in copper coils
- The arrangement of windings
- Type of material used in the motor
7.0Types of Electric Motors
Electric Motors are basically of two types based on the current that is AC or DC, which are further divided into sub-types:
- DC Electric Motors: As the name suggests, it works on direct current (DC) electricity. It periodically changes the direction of current in the armature by the commutator and brushes. It is used in small devices like toys, fans, and electric windows of cars.
- AC Motors: AC Motors operates on alternating current (AC) electricity, a more commonly used electric motor in industrial and household usage. It is further divided into:
- Synchronous Motors: The rotor rotates at constant speed synchronously with the supply frequency.
- Induction Electric Motors: The rotor is induced by the magnetic field of the stator, and it rotates at a speed that is slightly lower than the synchronous speed.
- 3-Phase Electric Motor: A 3-phase electric motor is a class of AC motors powered by three-phase electric power. In this type of electric motor, three alternating currents, namely the ACs, travel to the motor. These three currents generate a rotating magnetic field within the motor. The rotation of this magnetic field causes the motor’s rotor to turn.
- 12V DC Electric Motor: Originally it is the smaller version of DC motors, which is powered by a 12V DC battery or power supply. It is widely used for low-voltage devices such as toys and model vehicles.
- Water Pump Electric Motor: It is the type of AC or DC motor specifically used in operating the water pump for irrigation, water supply, and drainage systems.
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9.0Supporting Study Materials
This study material CBSE Notes and NCERT Solutions for the Chapter "Magnetic Effects of Electric Current" on Electric Motor Topics is designed according to the latest CBSE Class 10 Science syllabus and NCERT guidelines. It provides clear explanations of key concepts, definitions, examples, and important questions to help students understand the working principle of an electric motor, Fleming's Left-Hand Rule, commercial motor features, and prepare effectively for examinations.
10.0
11.0Previous Year Questions (PYQs) on Electric Motor
Q1. State the principle of an electric motor. What is the specific functional role of a split-ring commutator in a DC motor? (CBSE Board)
Solution
- Principle of an Electric Motor: An electric motor operates on the principle that when a rectangular current-carrying coil is placed inside a magnetic field, it experiences a mechanical force due to the interaction of the magnetic fields. This force creates a torque that rotates the coil continuously.
- Role of a Split-Ring Commutator: The split-ring commutator acts as a mechanical rotary switch that reverses the direction of the electric current flowing through the armature coil after every half-rotation (180 degrees). By reversing the current, it ensures that the downward force stays on the left side and the upward force stays on the right side, allowing the motor to spin continuously in a single direction.
Q2. State Fleming's Left-Hand Rule. Explain how the armature coil in an electric motor manages to bypass the vertical position where current flow drops to zero. (CBSE Board)
Solution
- Fleming's Left-Hand Rule: Stretch the thumb, forefinger, and middle finger of your left hand perpendicular to each other. If the forefinger points in the direction of the external magnetic field and the middle finger points in the direction of the current, then the thumb indicates the direction of the motion or force acting on the conductor.
- Bypassing the Vertical Position: When the armature coil reaches a perfectly vertical position, the gaps between the split-ring segments align with the carbon brushes, breaking the electrical circuit and dropping the current to zero. The coil does not stall here because of its inertia of motion. The momentum gathered during the previous phase pushes the rotating assembly past this dead spot, allowing the split rings to reconnect with the brushes and resume rotation.
12.030-Second Revision: Electric Motor
- Electric Motor = Converts electrical energy into mechanical energy.
- Principle = A current wire experiences a physical force inside a magnetic field.
- Fleming's Left-Hand Rule = Thumb = Force/Motion, Index = Field, Middle = Current.
- Split-Ring Commutator = Reverses the current every half-turn to keep the motor spinning in one continuous direction.
- Brushes = Stationary carbon blocks that feed current into the rotating split rings.
- Inertia of Motion = Carries the motor past the vertical 90-degree spot where current drops to zero.
- Commercial Upgrade = Uses a soft iron core and electromagnets to maximize torque.
13.0Recommended Next Topics