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An '''electric motor''' is a device which converts electrical energy into kenetic and mechanical energy. Most electric motors utilise the [[motor effect]] in the collective deflection of a flow of electrons through a wire to turn a coil, however other models employ more ingenious devices such as the induction of [[eddy currents]].
==Basic Motors==
A basic motor consists of a coil placed in a magnetic field. As current passes through the coil it will experience a force such that one side of the coil will be deflected upwards and the other side downwards (as the current is running in opposite directions), resulting in the coil turning. When the coil turns such that is is parallel to the magnetic field (and hence no force of deflection) the direction of the current is reversed, both sides of the coil will now experience a force in the opposite direction, resulting in the coil continuing to turn. As the current is reversed every 180<sup>O</sup> turn of the coil it will continue to turn provided there is a power input.
The basic motor, whether DC or AC, consists of the following components:
* An armature, consisting of an axle, a coil and a commutator
** An axle, the rod containing the coil and the commutator which is also used to turn other components (such as a wheel). In some motors the rod will contain an iron section around which the coil is wrapped, increasing its induced magnetic field and hence the strength of the deflecting force
** A coil, or a length of wire looped many times, the current travels through this is deflected causing the coil to turn
** A commutator, through which current is fed to the motor and whose role is to keep current travelling in the same direction with respect to the stator field (and hence keeps the coil turning in the same direction). It is essentially a cylindrical conductor which receives current from the brushes. The type of commutator (split ring or slip ring) depends on the motor
* A stator component, consisting of a power supply, brushes and stator magnets
** The power supply is fed through the brushes, these push up against the commutator such that as it turns there is sufficient contact between the two surfaces to allow a decent current to flow
** Magnets, either permanent magnets or electromagnets, which provide the magnetic field (commonly called the stator field) which interacts with the induced field of the current, causing it to turn
The force on either side of the coil is given by ''F = nBIlsinX'' where n = number of coils, B = magnetic field density (tesla), I = current (amps), l = length of the wire (meters) and X is the angle of rotation of the coil (0<sup>O</sup> when the coil is parallel to the stator field, 90<sup>O</sup> when it is perpendicular to the field. This may seem contradictory, as in the motor effect a charged particle travelling parallel to a field will experience no force. However, the force on the coil is along the sides which are always perpendicular to the stator field, and hence will always experience a force, the reason the coil doesn't turn any further when it is at 90<sup>O</sup is because it has been deflected as far as it can go, and needs to have the current in the coil reversed to keep turning.
Torque is defined as the turning effect of the force, in this scenario it is the ability of the motor to do work (eg turn another object). ''Torque = Fs'' where s is the distance of the application of the force to the turning point (in this case the side of the coil to the axle). However, as there are two sides to consider the value of s is the length of the coil not affected by the field, hence allowing the derrivation of ''Torque = BIAcosX'' where A is the area of the coil. A motor with high torque will be able to exert a larger force on another object, in contrast a motor with low torque may not be able to carry much of a load. Torque is not related to speed, a motor can have a high turning speed and low torque, and vice versa.
==See Also==
* [[Electricity]]
* [[Motor Effect]]
[[Category:Technology]]
[[Category:Electricity]]
==Basic Motors==
A basic motor consists of a coil placed in a magnetic field. As current passes through the coil it will experience a force such that one side of the coil will be deflected upwards and the other side downwards (as the current is running in opposite directions), resulting in the coil turning. When the coil turns such that is is parallel to the magnetic field (and hence no force of deflection) the direction of the current is reversed, both sides of the coil will now experience a force in the opposite direction, resulting in the coil continuing to turn. As the current is reversed every 180<sup>O</sup> turn of the coil it will continue to turn provided there is a power input.
The basic motor, whether DC or AC, consists of the following components:
* An armature, consisting of an axle, a coil and a commutator
** An axle, the rod containing the coil and the commutator which is also used to turn other components (such as a wheel). In some motors the rod will contain an iron section around which the coil is wrapped, increasing its induced magnetic field and hence the strength of the deflecting force
** A coil, or a length of wire looped many times, the current travels through this is deflected causing the coil to turn
** A commutator, through which current is fed to the motor and whose role is to keep current travelling in the same direction with respect to the stator field (and hence keeps the coil turning in the same direction). It is essentially a cylindrical conductor which receives current from the brushes. The type of commutator (split ring or slip ring) depends on the motor
* A stator component, consisting of a power supply, brushes and stator magnets
** The power supply is fed through the brushes, these push up against the commutator such that as it turns there is sufficient contact between the two surfaces to allow a decent current to flow
** Magnets, either permanent magnets or electromagnets, which provide the magnetic field (commonly called the stator field) which interacts with the induced field of the current, causing it to turn
The force on either side of the coil is given by ''F = nBIlsinX'' where n = number of coils, B = magnetic field density (tesla), I = current (amps), l = length of the wire (meters) and X is the angle of rotation of the coil (0<sup>O</sup> when the coil is parallel to the stator field, 90<sup>O</sup> when it is perpendicular to the field. This may seem contradictory, as in the motor effect a charged particle travelling parallel to a field will experience no force. However, the force on the coil is along the sides which are always perpendicular to the stator field, and hence will always experience a force, the reason the coil doesn't turn any further when it is at 90<sup>O</sup is because it has been deflected as far as it can go, and needs to have the current in the coil reversed to keep turning.
Torque is defined as the turning effect of the force, in this scenario it is the ability of the motor to do work (eg turn another object). ''Torque = Fs'' where s is the distance of the application of the force to the turning point (in this case the side of the coil to the axle). However, as there are two sides to consider the value of s is the length of the coil not affected by the field, hence allowing the derrivation of ''Torque = BIAcosX'' where A is the area of the coil. A motor with high torque will be able to exert a larger force on another object, in contrast a motor with low torque may not be able to carry much of a load. Torque is not related to speed, a motor can have a high turning speed and low torque, and vice versa.
==See Also==
* [[Electricity]]
* [[Motor Effect]]
[[Category:Technology]]
[[Category:Electricity]]