When a current-carrying conductor is placed under a magnetic field, a force acts on the conductor. The direction of this force can be identified using Fleming’s Left Hand Rule. Likewise, if a moving conductor is brought under a magnetic field, electric current will be induced in that conductor. The direction of the induced current can be found using Fleming’s Right Hand Rule. 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. Fleming’s Left-Hand Rule is mainly applicable to electric motors and Fleming’s Right-Hand Rule is mainly applicable to electric generators.
Interpreting Fleming’s Right-Hand Rule
According to Faraday’s law of electromagnetic induction, when a moving conductor is placed inside a magnetic field, a current will be induced in it. If the conductor is forcefully moved inside the magnetic field, there will be a relationship between the direction of applied force, magnetic field and the current. This relation between these three directions is determined by Fleming’s right-hand rule.
“Hold the right hand fore finger, middle finger and the thumb at right angles to each other. If the forefinger represents the direction of the magnetic field, the thumb points in the direction of motion or applied force, then the middle finger points in the direction of the induced current.”
Interpreting 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 to the direction of the current flow. A left hand can be held, as shown in the illustration, so as to represent three mutually orthogonal axes on the thumb, forefinger and middle finger.
The left-hand rule requires you to
“Hold out your left hand with the forefinger, second finger and thumb perpendicular to each other. If the forefinger represents the direction of the field and the second finger represents that of the current, then thumb gives the direction of the force.”
Difference Between Fleming’s Left-Hand and Right-Hand Rule
It was invented by John Ambrose Fleming
|It was invented by John Ambrose Fleming|
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
From this, we can observe that the left hand satisfies Motor, and the right hand – Generator. The 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.
Want to learn more about the Magnetic Effects of Electric Current? Check out our learning app available for free download. Keep Learning with BYJU’s – The Learning App.