When a current-carrying conductor is placed in a magnetic field, a force acts on a conductor. The direction of force act can be identify by using Fleming’s Left Hand Rule. Like that, if a moving conductor is place under a magnetic field, electric current will be induced in this conductor. The direction of the induced current can be identify by using Fleming’s Right Hand Rule.
Fleming Left-Hand Rule is mainly applicable to electric motors to find direction of rotation and Fleming Right-Hand Rule is mainly applicable to find the direction of induce EMF in electric generators.
Fleming’s right hand rule:
The direction of dynamically induced EMF can be identified by using this rule.
Hold the thumb, forefinger and middle finger of the right hand at right angles with each other as shown in Figure Fleming’s right hand rule.
So that the forefinger indicate the direction of flux and the thumb indicate the direction of the motion of the conductor, then the middle finger indicates the direction of induced EMF. As per Fleming’s right hand rule.
The direction of induce EMF is towards the observer or away from the observer.
Consider a conductor moving in between magnetic field (north and south poles) in an anticlockwise direction as shown in Figure.
Now, applying Fleming’s right hand rule. We can find that the conductor ‘A’ which is moving upwards and flux flow from North to South Pole.
So the induce EMF in the direction towards the observer at ‘A’, indicated by the dot sign.
Now the conductor ‘B’ which is moving down and flux direction is same as above from north to south.
The induce EMF in the direction away from the observer indicated by the plus sign.
Figure shows the current direction in the form of an arrow. The dot sign indicates the pointed head of the arrow showing the current direction towards the observer.
And the plus sign indicates the cross-feather of the arrow tail showing the current direction away from the observer.
by using Fleming’s right hand rule we can find the direction of induced current in dc generator.
Fleming’s Left Hand Rule:
The direction of force exerted on a current carrying conductor placed in a magnetic field can be determined by using Fleming’s left hand rule.
Arrange thumb, forefinger and middle finger of the left hand mutually perpendicular with each other, such that the middle finger is in the direction of current flow through the conductor and forefinger is in the direction of flux. Then the thumb indicates the direction of motion of the conductor.
This is the statement of Fleming’s left hand rule.
For example, a loop of coil carrying current, when placed under north and south poles as shown in Figure, it rotates in an anticlockwise direction. Fleming’s left hand rule is used to find the direction of rotation in dc motor.
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