Fleming’s Left-Hand Rule and Fleming’s Right-Hand Rule are essential rules applicable in magnetism and electromagnetism. John Ambrose Fleming developed them in the late 19th century as a simple way of working out the direction of electric current in an electric generator or the direction of motion in an electric motor. It is important to note that these rules do not determine the magnitude; instead show only the direction of the three parameters (magnetic field, current, force) when the direction of the other two parameters is known.
| Table of Contents: |
What is Fleming’s Right-Hand Rule?
According to Faraday’s law of electromagnetic induction, when a conductor moves through a magnetic field, an electric current is induced in it. Fleming’s right-hand rule is used to determine the direction of the induced current.
Fleming’s Right Hand Rule states that if we arrange our thumb, forefinger and middle finger of the right-hand perpendicular to each other, then the thumb points towards the direction of the motion of conductor relative to the magnetic field, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the induced current.
What is Fleming’s Left-Hand Rule?
When a current-carrying conductor is placed in an external magnetic field, the conductor experiences a force perpendicular to both the field and the current flow’s direction. Fleming’s left-hand rule is used to find the direction of the force acting on the current carrying conductor placed in a magnetic field.
Fleming’s Left Hand Rule states that if we arrange our thumb, forefinger and middle finger of the left-hand perpendicular to each other, then the thumb points towards the direction of the force experienced by the conductor, the forefinger points towards the direction of the magnetic field and the middle finger points towards the direction of the electric current.
Difference Between Fleming’s Left-Hand and Right-Hand Rule
| Fleming’s Left-Hand Rule | Fleming’s Right-Hand Rule |
| It is used for electric motors | It is used for electric generators |
| The purpose of the rule is to find the direction of motion in an electric motor | The purpose of the rule is to find the direction of induced current when a conductor moves in a magnetic field. |
| The thumb represents the direction of the thrust on the conductor. | The thumb represents the direction of motion of the conductor. |
| The index finger represents the direction of the Magnetic Field. | The index finger represents the direction of the Magnetic Field. |
| The middle finger represents the direction of the current | The middle finger represents the direction of the induced current |
We can observe that the left-hand rule is applicable to Motors and the right-hand rule to Generators. Fleming’s left-hand rule and Fleming’s right-hand rule are a pair of visual mnemonics (mnemonics are learning techniques or memory aids, such as an abbreviation, rhyme or mental image that helps to remember something). In practice, these rules are never used except as a convenient trick to determine the direction of the resultant – either current or thrust. What gives the magnitude of force along this direction determined by these rules is the Lorentz’ Force.
After a quick revision of Magnetic Effects of Electric Current, the top five questions asked from the chapter Magnetic Effects of Electric Current are discussed in this video.
Fleming’s Left-Hand Rule Examples
Q1. Determine the direction of the force acting on the proton if the proton moves towards the east by entering a uniform magnetic field in the downward direction.
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. Consequently, we can say that the direction of the force acting is towards the north.
Q2. Find the direction of the magnetic field if an electron is moving vertically upwards and gets deflected towards the south due to a uniform magnetic field.
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.
Frequently Asked Questions – FAQs
State Fleming’s right hand rule.
State Fleming’s left-hand rule.
Which rule is used in electric motors?
What is the purpose of Fleming’s right hand rule?
Which rule is used for electric generators?
Keep Learning with BYJU’s – The Learning App!
Want to learn more about the Magnetic Effects of Electric Current? Check out our learning app available for free download.
Fantastic page
It’s very helpful page