# What causes the rotor in a DC motor to rotate in one direction only? What would happen if it rotated in the opposite direction?

What causes the rotor in a DC motor to rotate in one direction only? What would happen if it rotated in the opposite direction?

The interaction between the magnetic fields of the stator & the rotor causes the rotor of a DC motor to rotate in a single direction.

# Explanation

## Stator Magnetic Field

The stator of a DC motor includes either permanent magnets (or) electromagnets that provide a stationary magnetic field. This magnetic field is aligned from the north pole to the south pole of the stator.

## Rotor Magnetic Field

The rotor has windings that convey an electric current. This current generates a magnetic field surrounding the rotor that is perpendicular to the stator’s field.

## Torque Generation

The interaction of the stator’s and rotor’s magnetic fields produces a force causing the rotor to rotate. The right-hand rule describes this force: the thumb points to the force, the index finger points to the magnetic field, & the middle finger points to the current flow. This determines the direction of rotation.

## Unidirectional Rotation

The DC motor’s commutator and brushes make sure that the current in the rotor windings always flows in the same direction as the stator’s magnetic field. This keeps the rotor’s magnetic field & torque in the same direction, allowing it to rotate in only one direction.

If the polarity of the stator’s magnetic field (or) the direction of the rotor’s current were reversed, the rotor would rotate the opposite way. This is because the interplay of the magnetic fields would lead the rotor to feel an opposing force, causing it to rotate in the opposite direction.

To summarize, the unidirectional rotation of the DC motor rotor is caused by a consistent interaction between the stator’s magnetic field & the rotor’s magnetic field, which is kept stable by the commutator & brushes. Reversing the polarity of either the stator (or) the rotor causes the rotor to rotate in the opposite direction.