Question

State Fleming’s Left-Hand Rule and explain its application in an electric motor.

Hint:

Left Hand = Motor Rule. Thumb → Motion, Forefinger → Magnetic Field, Middle Finger → Current.

Answer 1

Concept: Fleming’s Left-Hand Rule gives the direction of the force acting on a current-carrying conductor placed in a magnetic field. It is based on the interaction between magnetic field and electric current, which produces mechanical force. Statement of Fleming’s Left-Hand Rule: If we stretch the thumb, forefinger, and middle finger of the left hand mutually perpendicular to each other, then:

• Forefinger represents the direction of the magnetic field (B),
• Middle finger represents the direction of current (I),
• Thumb represents the direction of force or motion (F) acting on the conductor.

Application in an Electric Motor: An electric motor works on the principle that a current-carrying conductor placed in a magnetic field experiences a force. Explanation:

• In a simple DC motor, a rectangular coil is placed between the poles of a magnet.
• When current flows through the coil, each side of the coil experiences a force due to the magnetic field.
• According to Fleming’s Left-Hand Rule, the direction of force on the two sides of the coil is opposite.
• These opposite forces form a couple, causing the coil to rotate.
• The split ring commutator reverses the direction of current after every half rotation, ensuring continuous rotation of the coil.

Conclusion: Fleming’s Left-Hand Rule helps determine the direction of motion of the coil in an electric motor. It explains how electrical energy is converted into mechanical energy.