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When a current-carrying conductor is placed in a magnetic field, the magnetic field exerts a force on it. A conductor moving in a magnetic field, on the other hand, induces an emf across the conductor (Faraday’s law of electromagnetic induction). John Ambrose Fleming proposed two rules to determine the direction of motion (in motors) or the direction of induced current (in generators).
Fleming’s left-hand rule and Fleming’s right-hand rule are the two rules (for generators). The right-hand rule of Fleming is mostly applicable to electric generators, while the left-hand rule is mostly applicable to electric motors. Both of these principles were proposed by John Ambrose Fleming in the late nineteenth century, and they are known as Fleming’s left and right-hand rule.
John Ambrose Fleming, a British physicist, devised the left-hand rule and the right-hand rule in the late 19th century.
Fleming's left-hand rule
Before understanding Fleming’s right-hand rule, let’s discuss the left-hand rule in detail!
A new conductor is exposed to a force that is perpendicular to both the magnetic field and the current direction when it is placed in a magnetic field.
According to Fleming’s left-hand rule, “If the thumb, forefinger, and left hand’s middle fingers are overextended perpendicular to each other, and the forefinger represents the magnetic field, the middle finger represents the current, then the thumb represents the force.”
For motors, Fleming’s left-hand rule applies.
Fleming’s Left Hand Rule: How Do You Keep It in Your Mind?
- The thumb corresponds to thrust, the forefinger to the field, and the centre finger to current.
- The thumb represents the thrust direction of the conductor.
- The forefinger represents the direction of the magnetic field.
- The centre finger directs the current (middle finger).
Fleming’s right-hand rule
Fleming’s right-hand rule is employed in generators. Fleming’s right-hand rule is used when a conductor travels in a magnetic field region to identify the route of induced current in the conductor. When a conductor coupled to a circuit travels in a magnetic field, the rule displays the path of the induced current. When a closed circuit exists, the Fleming right-hand rule can determine the direction of current in a generator’s windings. Faraday’s law of induction causes the EMF to be induced in the coil. The direction of current flow in the generator winding can also be determined using the Fleming right-hand rule. Normally There are two types of currents that can flow through a coil or conductor.
To use the right-hand rule, the right hand must be held the same way as the left. As a result, the right hand is simply a reflection of the left. Another way to demonstrate this is to hold the right hand with the thumb’s first and second fingers perpendicular to each other (at right angles). It can be used to recall the following things while in this position:
- The thumb represents the conductor’s direction of motion.
- The first finger shows the field’s direction. (From north to south.)
- The second finger represents the induced or generated current (the direction of the induced current will be the direction of conventional current; from positive to negative).
Know the Difference Between Fleming's Left Hand and Right-Hand Rules
Let’s look at the difference between Fleming’s Right-hand rule and left-hand rule.
Right-Hand Rule | Left Hand Rule |
Electric generators are made of this material. | The term “eclectic motor” is used to describe a variety of motors |
In eclectic generators, it’s used to determine the direction of induced EMF and current. | In electric motors, this is used to determine the direction of motion and current. |
The conductor’s motion in a magnetic field is depicted by the thumb. | The direction of applied force or motion is indicated by the thumb. |
The first (index of the forefinger) reveals the magnetic force lines’ direction (flux). | The first (index of the forefinger) reveals the magnetic force lines’ direction (flux). |
The direction of induced EMF and current is shown by the second (middle) finger. | The direction of the current is indicated by the second (middle) finger. |
In this rule, the right hand is employed for generators. | In this rule, the left hand is employed for motors. |
Conclusion
The left-hand rule applies to motors, while Fleming’s right-hand rule applies to generators. The left-hand rule and the right-hand rule are two visual mnemonics devised by Fleming (mnemonics are learning techniques or memory aids, such as an abbreviation, rhyme, or mental image that helps to remember something). In practice, these criteria are only employed to determine the consequent direction – either current or push – as a convenient gimmick.
