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What does the middle finger represent in Fleming's Left-Hand Rule?
Direction of magnetic field
Direction of induced EMF
Direction of current
Direction of force
Direction of current
Fleming's Left-Hand Rule is a mnemonic used to determine the direction of the force acting on a current-carrying conductor placed in a magnetic field. In this rule, the middle finger of the left hand is specifically aligned to point in the direction of the electric current.
Fleming's Left-Hand Rule is a mnemonic used to determine the direction of the force acting on a current-carrying conductor placed in a magnetic field. In this rule, the middle finger of the left hand is specifically aligned to point in the direction of the electric current.
Think of it like a three-dimensional corner of a room: the floor corner where the walls meet is the origin, with the three edges representing the three mutually perpendicular vectors of force, field, and current.
FBI (Thumb = Force, Forefinger = B-field, middle finger = I-current).
F=I(L├ЧB) тАФ Force on a current-carrying conductor in a magnetic field
F=q(v├ЧB) тАФ Lorentz force on a moving charge
The rule is based on the Lorentz Force principle, where a charged particle moving through a magnetic field experiences a force perpendicular to both the velocity of the charge and the magnetic field. When the thumb, index finger, and middle finger are held mutually perpendicular, the index finger represents the magnetic field (B), the middle finger represents the current (I), and the thumb indicates the direction of the magnetic force (F).
The fingers must be held mutually perpendicular to each other.
This rule is specifically for electric motors where current is supplied to produce motion.
It is the converse of Fleming's Right-Hand Rule, which is used for generators.
Provides a simple visual method to predict the motion of motors.
Easy to implement without complex vector calculations for simple orientation problems.
Only applicable when vectors are mutually perpendicular.
Requires manual dexterity to position fingers correctly.
Working principle of DC motors.
Design of moving-coil galvanometers and loudspeakers.
| Feature | Left-Hand Rule | Right-Hand Rule |
|---|---|---|
Rule Application | Electric Motor | Electric Generator |
The index finger (Forefinger) always represents the magnetic field (B), which points from North to South.
Option A is incorrect because the index finger represents the magnetic field. Option B is incorrect as induced EMF relates to Fleming's Right-Hand Rule. Option D is incorrect because the thumb represents the force.
C is correct тАФ The middle finger of the left hand points in the direction of the conventional current flow.
Always remember: Left-Hand for Motors (input current, output force) and Right-Hand for Generators (input force, output current/EMF).