A current-carrying conductor in a magnetic field can experience a force, with an equal opposite force on the field-producing magnet. Fleming’s left-hand rule links field, conventional current and force: first finger field, second finger current, thumb force. Reversing either field or current reverses force; reversing both restores its direction. The force is greatest with the conductor perpendicular to the field. Example: State what the thumb represents. Force or motion. Consider the conditions.