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Which of the following law/rule can be used to determine the direction of rotation of DC motor?
Lenz's law
Faraday's law
Coloumb's law
Fleming's left-hand rule
Fleming's left-hand rule
Fleming's left-hand rule is specifically used to determine the direction of force (and thus rotation) on a current-carrying conductor placed within a magnetic field, which is the foundational principle of a DC motor. When current flows through the armature conductors in a magnetic field, the motor action is described by the interaction between the field flux and the conductor current.
Fleming's left-hand rule is specifically used to determine the direction of force (and thus rotation) on a current-carrying conductor placed within a magnetic field, which is the foundational principle of a DC motor. When current flows through the armature conductors in a magnetic field, the motor action is described by the interaction between the field flux and the conductor current.
F=BIlsin╬╕ тАФ Force on a current-carrying conductor
╧Д=KtтАЛ╬жIaтАЛ тАФ Electromagnetic torque of a DC motor
According to the rule, if you hold the thumb, index finger, and middle finger of your left hand mutually perpendicular to each other, the index finger points in the direction of the magnetic field, the middle finger points in the direction of the current, and the thumb indicates the direction of the resultant mechanical force. In a DC motor, this force creates the torque that causes the armature to rotate.
Used for DC motors (motor action).
Thumb represents the direction of motion or force.
Index finger represents the direction of the magnetic field.
Middle finger represents the direction of the current flow.
Simple mnemonic for field-current-force relationship
Applicable to all DC machine calculations
Not applicable for generators (requires Right-Hand rule)
Only provides direction, not magnitude
DC motor design and analysis
Electromagnetic actuators
Relays and solenoid mechanisms
Lenz's Law is used to determine the direction of induced EMF in a circuit (Generator action).
Faraday's Law describes the magnitude of induced EMF.
Coulomb's Law relates to electrostatic force between charges.
D is correct тАФ Fleming's left-hand rule is the standard method for determining the direction of force on a current-carrying conductor in a magnetic field.
Always remember: 'Left for Load' (Motors) and 'Right for Result' (Generators/Induced Current) to distinguish between Fleming's rules.