Fleming’s Left Hand Rule and Right Hand Rule

In this article, we will learn about two fundamental Fleming rules given by John Ambrose Fleming, known as Fleming’s Left Hand Rule and Fleming’s Right Hand Rule. These two rules are widely used in electrical machines to determine the direction of motion of the rotor and the direction of induced current in a generator. However, it is important to note that these rules do not determine the magnitude of the force or current. Let’s discuss these rules in detail.

What is Fleming’s Left Hand Rule?

In an electromagnetic system, when a conductor carrying an electric current is placed in a magnetic field, a force will act on the conductor. The direction of the force on the conductor will be perpendicular to the direction of both the magnetic field and the electric current.

Let us now discuss the statement of Fleming’s left-hand rule.

Statement of Fleming’s LeftHand Rule:

Fleming’s left-hand rule states that if we stretch the thumb, forefinger, and middle finger of the left hand such that they are perpendicular to each other. If the forefinger points the direction of the magnetic field and the middle finger points the direction of the electric current through the conductor. Then, the thumb will point in the direction of force acting on the conductor placed in the magnetic field.

This statement is illustrated in the following figure.

It is important to note that Fleming’s left-hand rule is used in electric motors to determine the direction of rotation.

Example based on Fleming’s Left Hand Rule:

Consider two current-carrying conductors, “a” and “b,” placed in a magnetic field, as shown in the following figure.

The direction of current in the conductor “a” is outward of the plan of paper, while the direction of current in the conductor “b” is inward to the plan of paper.

Now, if we apply Fleming’s left-hand rule to the conductor “a,” where the direction of the magnetic field is represented by the forefinger finger and the direction of the current is represented by the middle finger. Then, the direction of force acting on the conductor “a” will be represented by the thumb, which is in the downward direction.

Similarly, if we apply Fleming’s left-hand rule to the conductor “b,” then the direction of force acting on the conductor will be upward.

This is how we can use this rule to determine the direction of force acting on a current-carrying conductor placed in a magnetic field.

Application of Fleming’s Left Hand Rule

We can determine the direction of the electromagnetic force acting on the conductor placed in a magnetic field using Fleming’s left-hand rule.

Let us now understand Fleming’s Right Hand Rule.

What is Fleming’s Right Hand Rule?

In an electromagnetic system, when there is a change in the magnetic field linked to a conductor, an EMF is induced in the conductor. If the circuit is closed, there will be an induced current in the conductor.

The direction of the induced current in the conductor is perpendicular to the direction of the motion of the conductor and the direction of the magnetic field.

Statement of Fleming’s Right Hand Rule:

According to Fleming’s right-hand rule, if we stretch the thumb, forefinger, and middle finger such that they are perpendicular to each other. Then, if the thumb represents the direction of motion of the conductor and the forefinger represents the direction of the magnetic field. The middle finger will point in the direction of the induced current in the conductor.

It is important to note that Fleming’s right-hand rule is used to determine the direction of induced current in electric generators.

Let us consider an example to understand the application of Fleming’s right-hand rule.

Consider a conductor moving in the upward direction and is placed in a magnetic field, as shown in the following figure.

If we apply Fleming’s right-hand rule, we get that the direction of induced current in the conductor is inward to the plan of paper.

Application of Fleming’s Right Hand Rule

Fleming’s right-hand rule is used to determine the direction of induced current in a conductor moving in a magnetic field. It is also applicable to determine the direction of current in a generator’s windings.

Conclusion

In conclusion, Fleming’s left-hand and right-hand rules are fundamental rules used in electrical machines, motors, and generators to determine the direction of motion or direction of induced current. Fleming’s left-hand rule is used in electric motors to determine the direction of rotation of the rotor. In contrast, Fleming’s right-hand rule is used in electric generators to determine the direction of induced current.