The difference between Fleming Left Hand and Fleming Right Hand Rule ( pHysics)

Hello students,

Ever wondered why Fleming Left Hand Rule and Fleming Right Hand Rule are actually useful?

First off, here are the background of Fleming Left Hand Rule:

Fleming Left Hand Rule

Fleming Left Hand Rule and Fleming Right Hand Rule are merely visual mnemonics. They are not the reasons why your motion of motor is likewise or whether it is the reason why your electric current flows the way it is in your generators.

They are simply means to memorize.

Fleming Right Hand Rule

Fleming's left-hand rule and Fleming's right-hand rule were originated by John Ambrose Fleming, in the late 19th century, as a simple way of working out the direction of motion in an electric motor, or the direction of electric current in an electric generator.



When current flows in a wire, and an external magnetic field is applied across that flow, the wire experiences a force perpendicular both to that field and to the direction of the current flow. A left hand can be held, as shown in the illustration, so as to represent three mutually orthogonal axes on the thumb, first finger and middle finger. Each finger is then assigned to a quantity (electric current, magnetic field and mechanical force). The right and left hand are used for generators and motors respectively


Students tend to be confused on when to use either one as both have the same things on each thumb, forefinger and middle finger!

LEFT HAND RULE ( MOTOR):

Essentially, the Left hand rule is used to figure out the motion resulted from the electromagnetism, in motor circuits (here, we have electric energy changed to kinetic energy)

The Left Hand Rule is used when some information of the circuit is provided (current and magnetic field) and often you are required to find the direction of motion of force.

RIGHT HAND RULE (GENERATOR):

The Right Hand rule is used in generator circuits where kinetic energy is changed to electric.

Often you are given information on the magnetic field and a rotating wire (such as a dynamo or an electric generator) and you are required to find the direction of e.m.f. or the direction of (electric) current.


DISTINGUISHING BETWEEN THEM:

In an electric motor, the electric current and magnet field exist (which are the causes), and they lead to the force that creates the motion (which is the effect), and so the left hand rule is used.

In an electric generator, the motion and magnetic field exist (causes), and they lead to the creation of the electric current (effect), and so the right hand rule is used.


LEFT MOTOR, RIGHT GENERATOR:

If you are confused when to use which just remember the rule for motors can be recalled by remembering that "motors drive on the left in Britain".  The rule for generators can be recalled by remembering that either the letters "g" and "r" is common to both "right" and "generator", or the phrase "Jenny is always right" ("Genny" being a common shortened version of Generator).