Which rule determines the direction of movement of a current-carrying conductor in a magnetic field?

Which rule determines the direction of movement of a current-carrying conductor in a magnetic field?

• A. Left-hand Rule
• B. Right-hand Rule
• C. Fleming's Left-Hand Rule
• D. Lenz's Law

Answer: (A)

Fleming’s Left-Hand Rule tells you how a current-carrying conductor behaves in a magnetic field. If you point your left-hand index finger in the direction of the magnetic field (B), your middle finger in the direction of conventional current (I), your thumb will point in the direction of the force (F) acting on the conductor, i.e., the direction the conductor will move. This follows from the cross product relationship F ∝ I × B, which makes the force perpendicular to both current and field. The right-hand rule is used for generators or the general cross-product direction in other contexts, and Lenz’s Law concerns the direction of induced current to oppose changes in magnetic flux, not the motion of a straight conductor. So the motor-case rule—the left-hand rule—gives the correct direction of movement.

Fleming’s Left-Hand Rule tells you how a current-carrying conductor behaves in a magnetic field. If you point your left-hand index finger in the direction of the magnetic field (B), your middle finger in the direction of conventional current (I), your thumb will point in the direction of the force (F) acting on the conductor, i.e., the direction the conductor will move. This follows from the cross product relationship F ∝ I × B, which makes the force perpendicular to both current and field. The right-hand rule is used for generators or the general cross-product direction in other contexts, and Lenz’s Law concerns the direction of induced current to oppose changes in magnetic flux, not the motion of a straight conductor. So the motor-case rule—the left-hand rule—gives the correct direction of movement.