Electric Motor Explained: Working Principle, Diagram, Types & Real-Life Uses

🔍 Definition of Electric Motor

An electric motor is a device that converts electrical energy into mechanical energy. It works based on the principle of electromagnetism — when a current-carrying conductor is placed in a magnetic field, it experiences a force that causes motion.

⚙️ Working Principle of Electric Motor

The electric motor works on Fleming’s Left-Hand Rule. When electric current flows through a coil in a magnetic field, it experiences a mechanical force that causes it to rotate.

Formula:

F= BIL Sin(θ)

Where:

• F = force
• B = magnetic field strength
• I = current
• L = length of conductor
• θ = angle between conductor and magnetic field

🖼️ Diagram Description (Simple DC Motor)

Imagine this:

• A rectangular coil is placed between the poles of a magnet.
• The coil is connected to a battery through a commutator and brushes.
• When current flows, one side of the coil is pushed up and the other down, causing the coil to rotate.

📌 Rotation continues due to the commutator reversing current every half-turn.

WORKING PRINCIPLE OF MOTOR

The electric motor works on the principle that when a coil is placed in the magnetic field and the current passes through it resulting in rotation of the coil.

• When the current begins to flow, current flows through brush X, then A to B, B to C, C to D and then to brush Y and into the battery.
• Now applying Fleming’s Left Hand Rule to wire AB, Current is along AB, Magnetic Field is as shown (North-> South), the motion of the wire is downwards.
• Now applying Fleming’s Left Hand Rule to wire CD, Current is along CD, Magnetic Field is as shown (North-> South), the motion of the wire is upwards.
• The rectangular coil begins to move in the anti-clockwise direction
• Note that during anti-clockwise motion, the split rings and axle also move, whereas the brushes don’t move.
• After half a rotation, Wire CD and Split ring Q moves to the left. Wire AB and Split ring P moves to right. Brushes X and Y donot move.
• Now applying Fleming’s Left Hand Rule to wire CD, Current is along DC. (Battery -> Split ring Q -> DC , Magnetic Field is as shown (North-> South), the motion of the wire is downwards.
• Now applying Fleming’s Left Hand Rule to wire AB, Current is along BA. (Battery -> Split ring Q -> DC –> CB -> BA –> Split ring P) , Magnetic Field is as shown (North-> South), the motion of the wire is upwards.
• So, again the coil rotates in the anti-clockwise direction.
• The reversal of current in the coil results in the continous rotation of the coil. The reversal of current is achieved by the commutator rings

Simple Explanation Step-by-Step

1. Current Flow: When electric current is passed through the motor’s coil (armature winding), it generates a magnetic field around the coil.
2. Interaction with Magnetic Field: The motor also has permanent magnets or electromagnets that provide a static magnetic field.
3. Magnetic Force: The magnetic field of the coil interacts with the external magnetic field, producing a Lorentz force on the sides of the coil due to opposite current directions.
4. Rotation: The coil experiences force in opposite directions on either side, creating a torque that causes it to rotate.
5. Commutator Role: In a DC motor, a commutator reverses the direction of current every half-turn, ensuring continuous rotation in one direction.

🧰 Types of Electric Motors

1. AC Motor
   • Runs on alternating current
   • Used in household appliances
2. DC Motor
   • Runs on direct current
   • Used in toys, tools, electric vehicles
3. Synchronous Motor
   • Rotor speed equals supply frequency
4. Induction Motor
   • Most commonly used
   • Works without physical connection to rotor

✅ Advantages of Electric Motors

• High efficiency
• Low maintenance
• Eco-friendly (no emissions)
• Fast and smooth operation
• Long life and reliability

⚠️ Disadvantages of Electric Motors

• Initial cost can be high
• Requires constant power supply
• May overheat under load
• Speed control is complex (for some types)

🔌 Uses of Electric Motor

• Ceiling fans and pumps
• Washing machines
• Electric vehicles (EVs)
• Lifts and cranes
• Industrial machinery
• Robotics and automation

❓ FAQs on Electric Motors

Q1. Who invented the electric motor?
👉 Michael Faraday in the 1820s.

Q2. What is the role of a commutator in a DC motor?
👉 It reverses current direction every half-turn to keep the motor spinning in the same direction.

Q3. Where are induction motors commonly used?
👉 In industries and appliances like refrigerators and air conditioners.

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