Physics is a field full of interesting and practical concepts and theories. One of those practical theories is known as Fleming’s Left-Hand Rule and Fleming’s Right-Hand Rule. Let’s get to know what these rules are!
John Ambrose Fleming introduced fleming's left-hand rule and Fleming's right-hand rule during the end of the 19th century. He named both of these rules after his name. They are kind of some essential rules we apply in magnetism and electromagnetism.
These rules also help identify the direction of motion in electric motors and the direction of electric current in electric generators. You will always see a relation between the current, force, and magnetic field in both these rules.
However, you should know that these rules do not help determine the magnitude. They only show the direction of force, current, and magnetic field (the three parameters). These parameters can only be found if the direction of the other two parameters is known.
Below, we will explain Fleming's left-hand rule and Fleming's right-hand rule in detail, along with some examples. Keep Reading!
What is Fleming's Right-Hand Rule?
According to
Faraday's law of electromagnetic induction, an electric current is induced in a conductor when it passes through a magnetic field. Therefore, Fleming's right-hand rule is to find the direction of the current that is induced.
Fleming's right-hand rule states:
"If we place the middle finger, thumb, and forefinger of the right-hand perpendicular to each other, the middle finger will direct towards the induced current direction, the thumb will direct towards the direction of the motion conductor relative to the magnetic field, and the fore-finger directs towards the magnetic field's direction."
What is Fleming's Left-Hand Rule?
When a conductor with current inside is placed in a magnetic field, the conductor goes through a force that is perpendicular to the current flow's direction and the field. Hence, Fleming's left-hand rule can determine the direction of the force acting on the conductor in that external magnetic field.
Fleming's left-hand rule states:
"If we place the forefinger, thumb, and middle finger of our left-hand perpendicular to each other, then the forefinger will direct towards the direction of the magnetic field, the thumb will direct towards the direction of the force the conductor experiences, and the middle finger will direct towards the electric current's direction."
Difference Between Fleming Left-Hand Rule and Right-Hand Rule
Now that we have gone through Fleming's left-hand rule and Fleming's right-hand rule, it is time to go through some points that make these two distinguish from each other. Here you go:
Fleming's left-hand rule | Fleming's right-hand rule |
This rule is used solely for electric motors. | This rule is used solely for electric generators. |
The primary use of this rule is to find the direction of motion in electric motors. | The primary use of this rule is to find the induced current's direction when a conductor is moving in the magnetic field. |
In this rule, the thumb represents the direction of the conductor's thrust. | In this rule, the thumb represents the motion's direction of the conductor. |
The index finger or fore finger represents the direction of the magnetic field. | The index finger or fore finger represents the magnetic field's direction. |
The second finger or middle finger represents the current's direction. | The middle finger or second finger represents the induced current's direction. |
By going through the above text, you will probably know by now that the left-hand rule is only applicable to motors, and the right-hand rule is only applicable to generators. These two rules are nothing more than visual mnemonics. Visual mnemonics are creative memory aids like Rhymes, images, and abbreviations to remember and absorb something into your mind. Practically, you never really use these magnetic field rules. These rules are only used as a trick to find the direction of the current or thrust in the magnetic field.
Fleming's Left-Hand and Right-Hand Rule Examples
Example 1:
If a proton is moving towards the east and enters a uniform magnetic field in the downward direction, what will be the direction of the force acting on that proton?
Solution:
We can find the direction of the force acting on the proton with the help of Fleming's left-hand rule.
We know that the proton is moving to the east; hence, the current's motion is also going towards the east, right? Also, the direction of the magnetic field is downwards, and the direction of the force is towards the north. With that being said, we can clearly determine that the direction of the force acting on the proton is towards the north.
Example 2:
If an electron is vertically moving upwards and then deflects towards the south by a uniform magnetic field, what will be the direction of the magnetic field?
Solution:
We can find the direction of the magnetic field on the electron using Fleming's left-hand rule.
It is evident that the electron has a negative charge, right? When the electron moves upwards, the direction of the current will go in the opposite direction. Hence, the direction of the current will be downwards. We also know that the force on the electron is in the south direction. With that being said, the direction of the magnetic field will be towards the east.
Example 3:
In the image below, If the current, I, flowing in the straight and current-carrying wire starts decreasing, what will be the direction of the current induced in the metallic square placed right at its side?
Solution:
Keeping in mind the right-hand rule, the magnetic field of the straight wire is being perpendicularly directed to the plane of the square loop, and the magnetic flux of the wire is decreasing. The induced current stops this decrease in the magnetic flux in the loop. The induced current does this by producing a new magnetic field in the direction of the wire's magnetic field. Now, again considering the right-hand rule, the direction of the current in the loop of this inward magnetic field will be clockwise.
Final Words
Fleming's left-hand rule and the right-hand rules are straightforward. We hope that this post helped you easily understand the basic concept of Fleming's rule. If you still have any doubts and confusion, you can always take the help of our highly qualified and professional tutors to clear your concepts. Your private
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Frequently Asked Questions
What is Fleming's right-hand rule?
Fleming's right-hand rule states If we place the middle finger, thumb, and forefinger of the right-hand perpendicular to each other, the middle finger will direct towards the induced current direction, the thumb will direct towards the direction of the motion conductor relative to the magnetic field, and the fore-finger directs towards the magnetic field's direction.
What is Fleming's left-hand rule?
Fleming's left-hand rule states that If we place the forefinger, thumb, and middle finger of our left-hand perpendicular to each other, then the forefinger will direct towards the direction of the magnetic field, the thumb will direct towards the direction of the force the conductor experiences, and the middle finger will direct towards the electric current's direction.
Which rule is specifically for electric motors?
Fleming's left-hand rule is specifically used for electric motors.
Why do we use Fleming's right-hand rule?
We use Fleming's right-hand rule to find the direction of the current induced when a conductor is moving into a magnetic field.
Which rule is specifically for electric generators?
Fleming's right-hand rule is specifically for electric generators.
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