What Is the Role of the Magnetic Field in DC Electric Motors?
DC electric motors use rotating coils of wire driven by a magnetic field on a direct current. This process of movement combined with a direct current transforms electrical energy into mechanical energy. The magnetic field in these circuits is produced by direct currents, either macroscopic in wires, or microscopic currents produced by the electrons surrounding atom orbits.
The interaction between the magnetic field and the charge of the circuit is vital to the practical applications of the DC electric motor. Each magnetic field is dipolar, with opposing north and south poles. Magnetic fields can be found in single wires, in the coils of wire used to power machines, in the bar magnets we are all familiar with, and in the core of the earth. The wire coil used in DC motors is also known as the rotor or armature, and the pull of the opposing poles is known as the torque.
Most machines also contain another magnet called the stator, as it is permanently fixed in one place, as opposed to the constantly moving rotor. The rotor works against the magnetic field of the permanently fixed magnet to produce mechanical energy and motion. The rotor is also classified as an electromagnet because its field of magnet is the result of a direct current running through the wires. This means that no magnetic field is produced when the DC electric motor is turned off and not in use.
These circuits produce mechanical energy by working with the basic principles of magnetism, that a permanent magnet will attract and hold other metal objects in close range. This is because of the inherent quality of magnets referred to as the "magnetic field." In permanent magnets the attracting force is very simple; there is a clear movement of attraction from the North Pole to the south. In electromagnets, however, the movement of the "lines of flux" is more complicated.
Because electromagnets are in constant motion with the direct current running through them, the magnetic flux is also constantly moving. Depending on the direction of the current, concentric circles of magnetic attraction are set up around the conductor. This changing magnetic field produces, in turn, an electric field. This generation of a different energy field is characterised by Faraday's Law which states that the electromotive force of any closed circuit is proportional to the rate of change of the magnetic flux, and is essential to the running of DC electric motors.
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