Wheels of Barlow - definition

The Barlow Wheel is a demonstration electric motor that illustrates the action of the Lorentz force in a magnetic field on a conductor with current. It typically consists of a metal wheel mounted on a pivot, the rim of which is partially immersed in a conductive electrolyte (usually a sulphuric acid or salt solution) placed in a vessel. Underneath the wheel is a permanent permanent magnet that creates a magnetic field perpendicular to the plane of rotation of the wheel.

When an electrical voltage is applied to the rotating wheel - one supplying the wheel arm and the other in contact with the electrolyte - a current flows through a section of conductor. In the presence of a magnetic field, a Lorentz force is generated, acting on the conductor segment in the area immersed in the electrolyte, which causes a torque and sets the wheel in motion.

The Wheels Barlow wheel is often used as a didactic model in teaching the fundamentals of electrodynamics, as it is one of the first practical devices to illustrate the direct interaction of magnetic field and electric current. The rotational motion of the wheel follows from the fundamental principles of electromagnetism and is closely related to the left-hand rule (for motors) and the direction of current flow relative to the magnetic field lines.

From a physical point of view, this device is a simplified form of DC motor, lacking the commutator and the complex geometry of the windings. Its historical significance stems from the fact that it was one of the first systems used by Humphry Davy and Peter Barlow to empirically confirm the theory of electromagnetism in the 19th century. Today, in addition to its educational functions, the Wheels are sometimes analysed in the context of contact forces, electrolytic resistance and energy losses due to the resistance of a conducting fluid.

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