Electric Motor- Definition, Explanation

Introduction: 

In our daily life, we use many electrical appliances like Fan, Mixer Grinder, Washing Machine, Drilling machines, etc. In these appliances, a component of the appliance consumes electricity to rotate other parts attached to it. This component is known as an electric motor. An electric motor converts the electrical energy supplied into mechanical energy. 

Explanation: 

Parts of an Electric Motor: 

Magnets: The motor has a couple of magnets that produce a uniform magnetic field. 

Armature Coil: A rectangular current-carrying wire called the Armature coil of the motor. 

Split rings type commutator segments: They reverse the direction of current. 

Brushes: Split rings are connected to conducting Brushes. 

Battery: A source of current. 

Working of Electric Motor: 

Initially, the direction of current is clockwise, and the direction of the magnetic field is from N-pole to its S-pole. We see that for the two sides marked as left and right side the angle between the magnetic field and current is 90^o. In this situation, these two sides will experience the maximum force. Whereas for the remaining two sides, the angle between the magnetic field and current is 0^o or 180^o. Therefore, these two sides will experience no force. 

On Applying Fleming’s left-hand rule to the sides of the rectangular coil. We see that the force on the left side is upwards whereas on the right side is downwards. This makes the coil rotate in a clockwise direction. 

When the coil reaches the vertical position during rotation, the rectangular conducting coil is disconnected from the two commutator rings. The rectangular coil does not stop rotating even though the current to it is cut off because it has already acquired momentum and it moves beyond the vertical position. 

After half rotation, when the rectangular coil moves beyond the vertical position, the side which was earlier on the left side comes to the right side whereas the right side moves to the left side and the two commutator half rings automatically come in to contact with the coil. This reverses the direction of the current in the coil. 

The direction of force acting on the sides is switched when the direction of the current is reversed. As a result, the left side is pushed upward again, while the right side is pushed downwards. This causes the coil to revolve anticlockwise by half a turn. After every half rotation, the current in the coil is reversed, and the coil continues to revolve when electricity from the battery is delivered to it. 

The factors on which this rotating force depends. 

Observation 1: 

On increasing the magnetic field, the couple forces also increase. 

Observation 2: 

When the voltage or current is increased, the couple forces increase as well. 

Observation 3: 

When the number of turns in the coil is increased, the couple forces increase as well. 

In a Commercial Motor: 

• An electromagnet is used in place of a permanent magnet. 
• The coil is wound on a soft iron core. 

Summary

• Electric Motor: An Electric motor is a device that converts electrical energy into mechanical energy.
• Principle of an Electric Motor: An electric motor is based on a principle that when a current carrying conductor is placed in an external magnetic field it experiences a force,
• Working of an Electric motor: When a rectangular current carrying conductor is placed in a magnetic field a couple of forces act on it which try to rotate the conductor in a magnetic field. The directions of forces are given by Fleming’s left-hand rule.
• Fleming’s Left Hand Rule: It states that, If we hold the thumb, forefinger, and middle finger of the left-hand perpendicular to each other such that the forefinger points in the direction of the magnetic field, the middle finger points in the direction of the current, then the thumb shows the direction of force (motion) of the conductor.
• The efficiency of an electric motor can be increased by increasing the current in the coil, increasing the magnetic field, and increasing the number of turns in the coil.
• An electric motor is a part of many electrical appliances that we use in our daily lives, like fans, washing machines, grinders, and drilling machines, where it is required to convert some part of the electrical energy into rotational motion of a unit of the appliance.