Which rule uses the left hand to determine the direction of electron flow around a coil?

• A. Right hand rule
• B. Left hand rule
• C. Fleming's left-hand rule
• D. Coulomb's rule

Answer: (B)

The situation uses a hand rule to link three directions: the magnetic field, the motion or force on the conductor, and the direction of charge flow. Since electrons carry negative charge and move opposite to conventional current, the left-hand rule is the natural choice for tracking electron flow around a coil. If you orient your left hand so the forefinger points in the magnetic field direction (from north to south) and the middle finger points along the electron flow, the thumb will point in the direction of the force or motion on that wire segment. This directly tells you how the coil will move, because the motor effect causes a torque that drives rotation. The right-hand rule is used for conventional current in generators, Fleming’s left-hand rule is the motor rule tied to conventional current, and Coulomb’s rule deals with electrostatic forces, not the magnetic interaction of a current-carrying conductor in a field.