# Fleming’s Left Hand Rule and Fleming’s Right Hand Rule

Last Updated on November 1, 2023 by Electricalampere

Fleming’s left-hand rule is used to determine the direction of rotation of the rotor in electric motors while Fleming’s right-hand rule is used to determine the direction of induced current in electric generators.

John Ambrose Fleming established Fleming’s Left Hand Rule and Fleming’s Right Hand Rule.

In electrical machines, Fleming’s rules are commonly used to find out the direction of motion of the rotor and the direction of induced current in a generator. It’s important to understand that these rules only determine the direction and not the magnitude of the force or current.

Let’s dive into 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.

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

## Statement of Fleming’s LeftHand Rule:

According to Fleming’s left-hand rule, we can determine the direction of force acting on a conductor placed in a magnetic field by following a simple procedure.

First, we stretch out the thumb, forefinger, and middle finger of our left hand so that they are perpendicular to each other. Then, we point the forefinger in the direction of the magnetic field and the middle finger in the direction of the electric current through the conductor. Finally, the thumb will point in the direction of the force acting on the conductor. This rule makes it easy to understand the relationship between magnetic fields, electric currents, and the force they create.

We can better understand this rule through the diagram provided.

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

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

## Example based on Fleming’s Left Hand Rule:

Two conductors, “a” and “b,” carrying current are placed in a magnetic field shown in the figure.

The current in conductor “a” flows outward from the plane of paper, while the current in conductor “b” flows inward towards the plane of paper.

If we use Fleming’s left-hand rule to the conductor “a,” we can determine the direction of the force acting on it. According to the rule, the forefinger finger represents the direction of the magnetic field, while the middle finger represents the direction of the current. The thumb represents the direction of the force, which, in this case, is downwards.

Applying Fleming’s left-hand rule to conductor “b” indicates that the force acting on the conductor is upward.

## 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.

In an electromagnetic system, an EMF is induced in a conductor when there is a change in the magnetic field linked to it. The current will be induced if the circuit is closed. The current induced in a conductor is perpendicular to the conductor’s motion and the magnetic field.

## Statement of Fleming’s Right Hand Rule:

To determine the direction of the induced current in a conductor, we can use Fleming’s right-hand rule. First, we stretch out our thumb, forefinger, and middle finger so they are all perpendicular to each other. Next, we point our thumb in the direction of the conductor’s motion, and we point our forefinger in the direction of the magnetic field. Finally, the middle finger will point in the direction of the induced current in the conductor. This simple rule is a helpful tool for understanding current behavior in an electromagnetic field.

Fleming’s right-hand rule determines the direction of induced current in electric generators.

## Example based on Fleming’s Right Hand Rule:

To better understand how to apply Fleming’s right-hand rule, let’s consider an example.

When a conductor moves upward in a magnetic field, a force is generated in the conductor, as shown in the figure below.

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.

If we use Fleming’s right-hand rule, we can determine that the induced current in the conductor flows inward to the plane of the paper.

## Conclusion

To summarise, Fleming’s left-hand and right-hand rules determine the direction of motion or induced current in electrical machines, motors, and generators. In electric motors, Fleming’s left-hand rule determines the direction of rotation of the rotor, while Fleming’s right-hand rule determines the direction of induced current.