State Fleming’s Left-Hand Rule

Fleming’s left-hand rule states that:

When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and to the direction of the current flow.

It was invented by John Ambrose Fleming.

Illustration using the left hand

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. If we arrange the thumb, the center finger, and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the center finger gives the direction of current and the forefinger points in the direction of a magnetic field.


State Fleming’s left-hand rule


  • According to Faraday’s law of electromagnetic induction, when a moving conductor is placed inside a magnetic field, a current will be induced in it.
  • If the conductor is forcefully moved inside the magnetic field, there will be a relationship between the direction of applied force, magnetic field, and the current.
  • It is mainly used in the working of electrical motors.
  • The main purpose of the rule is to find the direction of motion in an electric motor.
  • The electric motor works on the principle of Faraday’s law of electromagnetic induction and the direction of motion in an electric motor is determined by this popular Fleming’s left-hand rule.

Application of Fleming’s left-hand rule

1. Using Fleming’s left-hand rule, we can determine the direction of force acting on the proton.

It is given that the proton is moving towards the east and therefore, the motion of the current is towards the east. The direction of force is towards the north as the magnetic field is acting downwards. Therefore, we can say that the direction of the force acting is towards the north.

2. Using Fleming’s left-hand rule, we can determine the direction of the magnetic field acting on the electron.

We know that the charge on an electron is negative. When the electron moves upward, the direction of the current is in the opposite direction, that is the direction of the current is downwards. It is given that the force acting on the electron is in the south direction. Therefore, the direction of the magnetic field is towards the east.

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