SUBJECT-MOTOR

Basic Working Principle of a Motor:
“When a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force.”
This force causes the conductor (usually a coil) to move, and this motion is what powers a motor.
Key Components of a Motor:
Stator – Stationary part that creates a magnetic field.
Rotor – Rotating part (attached to the shaft).
Commutator (in DC motors) – Reverses current direction.
Brushes – Maintain contact between power supply and rotating parts
Power Supply – Provides electrical energy (AC or DC).
Steps of Operation (DC Motor Example)
Electric current flows into the coil via brushes and commutator.
The coil is placed inside a magnetic field (created by the stator).
The current and magnetic field interact, creating a force on the coil (Lorentz force).
This force causes the coil (and rotor) to rotate.
The commutator switches current direction every half-turn to keep rotation continuous.
For AC Motors:
AC current alternates direction on its own, so commutators aren’t needed.
Rotating magnetic fields are created using alternating currents in stator windings.
How a Motor Starts Rotating (Step by Step)
Power is Supplied
When you switch on the motor, electric current flows into the motor’s coil (armature) through the brushes (in DC motors) or directly into the stator (in AC motors).
Magnetic Field is Created
The stator (either permanent magnets or electromagnets) creates a magnetic field around the rotor (the rotating part).
In AC motors, the stator winding itself generates a rotating magnetic field.
Current-Carrying Conductor in Magnetic Field
The rotor has coils (wires) that now carry current.
These current-carrying coils are placed inside the magnetic field.
Lorentz Force Acts
According to Lorentz force law:
A current-carrying conductor in a magnetic field experiences a force.
This force acts on the rotor coil, pushing it in a specific direction.
Rotor Starts to Rotate
The force causes rotational motion of the rotor.
In DC motors, the commutator switches the direction of current every half-turn to keep the rotation going in the same direction.
Summary:
A motor starts rotating when electric current flows through its coil inside a magnetic field, generating a force that causes the rotor to spin.