An electric motor is a device that converts electrical energy into rotational kinetic energy . A Simple d.c motor consists of a coil of insulated wire between two poles of a magnet as shown in figure below.
The coil ABCD can turn about a fixed axis within magnetic field provided by. a strong curved permanent magnet. Electric current enters and leaves the coil through a split ring P and Q which are refered to as the commutator.
The two half rings are insulated from each other and brushes slightly press against the commutator . Brushes are are then connected to the battery terminal.
we are assuming that the original position of the coil is at the horizontal position before the current is switched. The current flows in the direction indicated on the diagram when switch is closed. Using Fleming’s left hand rule, side AB experiences an upward force while side CD experiences a downward force.
Since the magnitude of current on both sides is the same, the forces on the sides are equal but opposite. The forces therefore causes the coil rotate in clockwise until it reaches it’s vertical position with side AB up. In this position, the brushes touch the space between the two halves of the split rings cutting off the current flowing hence no force is acting on the sides AB and CD at this position.
Electric motor Coil Rotation energy
Due to the rotational kinetic energy, the momentum in the coil carries it past this vertical position and the two split rings exchange brushes. The direction of the current through the coil is reversed and consequently direction of force on each side of the coil also changes direction. This process is refered as commutation.
Side AB is now on the right hand side while CD is on the left hand side. Side AB experiences a downward force while CD experience an upward force.
The coil ABCD will continue rotating in the clockwise so long as the current is flowing through it.
If current through the coil is increased, the coil rotates at much high speed. The speed of rotation is thus proportional to the strength of current flowing.
If the terminals of the battery are inter-changed, the direction of the current reverses and consequently direction of rotation of the coil reverses to the opposite direction.
How to make electric Motor more effective
The D.C motor described can be made more powerful by adjusting its setup in several ways that may include:
- winding the coil on a soft iron core so that iron core becomes magnetized and concentrates it’s magnetic field in the coil which greatly increases the force on the coil.
- Increasing the number of turns of the rotating coil which multiplies the force on the single coil by the number of turns made.
- using a stronger magnet to provide more powerful magnetic fields.
- Multiplying the number of coils and commutator segments.
- Replacing the permanent magnet by an electromagnet. This way the strength of the magnetic field can be adjusted as needed.
Related pages
- Magnetic effect of electric current
- Properties and principles of magnets
- Mutual Induction In electromagnetism
- An A.C. generator
- Magnetic fields
- Hans Christian Ørsted
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