Fleming’s Rules

Fleming’s rules can be define as

When a current-carrying conductor is place under a magnetic field, a force acts on the conductor. The direction of this force can be identify with Fleming’s Left Hand Rule.

Likewise,According to Fleming’s rules if a moving conductor is brought under a magnetic field. The electric current will be induce in that conductor.

Moreover, The direction of the induce current can be found using Fleming’s Right Hand Rule. It is important to note that these rules do not determine the magnitude. Instead show only the direction of the three parameters (magnetic field, current, force).

when the direction of the other two parameters is known.

In short there are two Fleming’s rules.

Fleming’s Left-Hand Rule is mainly applicable to electric motors and Fleming’s Right-Hand Rule is mainly applicable to electric generators.

Fleming's Rules

Fleming’s Right-Hand Rule

According to Faraday’s law of electromagnetic induction, when a moving conductor is place inside a magnetic field, a current will be induced in it. If the conductor is forcefully move inside the magnetic field, there will be a relationship between the direction of applied force, magnetic field and the current. Moreover, This relation between these three directions is determine by Fleming’s right-hand rule.

Fleming's rules
The thumb indicates the direction of the motion, the fore finger indicates the direction of the magnetic field and the middle finger represents the direction of the induced current.

As shown in the figure above, the right-hand rule requires you to

Hold the right hand fore finger, middle finger and the thumb at right angles to each other. If the forefinger represents the direction of the magnetic field, the thumb points in the direction of motion or applied force, then the middle finger points in the direction of the induced current.”

Fleming’s Left-Hand Rule

When a current-carrying conductor is place in an external magnetic field,  the conductor experiences a force perpendicular to both the 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, forefinger and middle finger.

Fleming's Left And Right Hand Thumb Rules Explained
The forefinger indicates the direction of the magnetic field, the middle finger indicates the direction of the current and the thumb represents the direction of the motion

The left-hand rule requires you to,

  • “Hold out your left hand with the forefinger, second finger and thumb perpendicular to each other. If the forefinger represents the direction of the field and the second finger represents that of the current, then thumb gives the direction of the force.”

Difference Between Fleming’s Left-Hand and Right-Hand Rule

Left-Hand RuleRight-Hand Rule
the phenomena was invent by John Ambrose FlemingThis phenomena was invent by John Ambrose Fleming
It is use for electric motorsIt is use for electric generators
The purpose of the rule is to find the direction of motion in an electric motorThe purpose of the rule is to find the direction of induce current when a conductor moves in a magnetic field.
thumb represents the direction of the thrust on the conductorthumb represents the direction of motion of the conductor.
index finger represents the direction of the Magnetic Fieldindex finger represents the direction of the Magnetic Field
middle finger represents the direction of the current middle finger represents the direction of the induced current

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