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In the context of electromagnetism, according to Fleming’s left-hand rule, the thumb indicates the ________.
direction of the magnetic field
length of the conductor
direction of the motion of the conductor
direction of the current
direction of the motion of the conductor
Fleming’s Left-Hand Rule is a mnemonic used to determine the direction of force experienced by a current-carrying conductor placed in a magnetic field. According to this rule, if the thumb, index finger, and middle finger of the left hand are held mutually perpendicular, the thumb indicates the direction of the force or the resulting motion of the conductor.
Fleming’s Left-Hand Rule is a mnemonic used to determine the direction of force experienced by a current-carrying conductor placed in a magnetic field. According to this rule, if the thumb, index finger, and middle finger of the left hand are held mutually perpendicular, the thumb indicates the direction of the force or the resulting motion of the conductor.
F=BIlsinθ — magnitude of the Lorentz force acting on the conductor
F=I(L×B) — vector form of the force on a current element
This rule is based on the Lorentz force principle, where a conductor carrying current I in a magnetic field of flux density B experiences a force F. The force is defined by the cross product F=I(L×B), where L is the vector representing the length of the conductor. The alignment of fingers ensures that the physical orientation matches the vector product results.
Thumb: Direction of Force (Motion of the conductor)
Index Finger: Direction of Magnetic Field (N to S)
Middle Finger: Direction of Current
The fingers must be held at 90° to each other
Simplifies visualization of motor operation
Provides a quick qualitative check for torque direction
Applicable only for DC motor applications
Requires careful orientation to avoid confusion with the Right-Hand Rule
Determining rotation direction in DC motors
Design of electromagnetic actuators and solenoids
| Feature | Fleming's Left | Fleming's Right |
|---|---|---|
Rule Type | Left-Hand Rule | Right-Hand Rule |
Fleming's Left-Hand Rule is strictly for motors (Motor effect), whereas Fleming's Right-Hand Rule is for generators (Generator effect).
Option A refers to the index finger, Option B is a physical property, and Option D refers to the middle finger.
C is correct — The thumb in Fleming's left-hand rule represents the direction of the force (motion) acting on the conductor.
Remember 'FBI': Forefinger (B/Magnetic field), Middle finger (I/Current), and thumb (F/Force) for the Left-Hand rule.
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