Posted on 04/03/2003 4:14:50 PM PST by vannrox
Ampère showed that two parallel wires carrying electric currents attract and repel each other like magnets. If the currents flow in the same direction, the wires attract each other; if they flow in opposite directions, the wires repel each other. From this experiment, Ampère was able to express the right-hand rule for the direction of the force on a current in a magnetic field. He also established experimentally and quantitatively the laws of magnetic force between electric currents.and that in this particular case the DC voltage was applied to produce an electrostatic field not to maintain an electric current. I read the actual paper and found that my interpretation of the slightly ambiguous sentence in question was, indeed, the correct one:
In all experiments, the surface-to-surface separation distance between spheres exceeded that for sparking in dry air by at least one order of magnitude. Surface-to-surface separation distances were typically larger than 5 mm. Also, the experiments were conducted in isolation from the surroundings by carefully insulating all fasteners and connectors, by utilizing a large open space, or by installing the experimental assembly in a Faraday box. Hence, current flow was negligible. We have found that our experimental model offers a particularly powerful approach to investigating electrostatic phenomena, and we have previously used similar setups to successfully calibrate the electrostatic force.1,2 The absence of electrical current and magnetic materials, natural or induced, leads us to conclude that the experimental assembly was electrostatic.
--Appl. Phys. Lett. 80, 2800 (2002), pp.2800-2801.
The spheres are stationary in both configurations, held in place by a combination of electrostatic, gravitational, and tension forces. Evidence for moment of force is based on experimental observations after 10, 20, and 200 h after voltage is applied to the center sphere at which times the spheres were deemed to be in static equilibrium. The experimental evidence for an electrostatic moment of force was as follows: 1. translational movement is not observed, 2. rotation about the vertical axis of the sphere proceeds until standstill where the induced moment of force is offset by the restoring torque of the suspending wire ~only after the external power supply is disconnected does the sphere return to its starting position, 3.the direction of the rotation remains invariant between replicate experiments, and 4. the magnitude of the net angular displacement increases with the length of the suspending wire.
We propose that rotation is the result of the continuum of static charges residing on the surface of the metal spheres. Theoretical evidence for rotation about the geometrical center of each sphere is obtained from the classical definition of the static moment of force, which, in the spirit of Cavendish and Coulomb, is determined from an action-at-a-distance perspective.
The correspondence between the theoretical prediction and the experimental observations lends considerable support to the notion that the rotation is an electrostatic entity. It is important to note that the direction of the rotation is explicit in the equation for moment of force. Rotation is either up or down, taken perpendicular to a plane passing through the sphere centers.
We have demonstrated a Coulomb motor where the moment of force is induced by an assembly of three spherical conductors held at constant potential. The rotation of the spheres about the axis perpendicular to the plane passing through the center of the spheres is shown to be a natural consequence of the electrostatic force. We find that when the charged spheres are stationary the only degree of motion that remains is rotation. Hence, the electrostatic coupling between the three charged spheres is converted to a net rotation beyond the observation that the rotation is likely to be general. The Coulomb motor appears to be feasible in systems ranging in size from molecular to macroscopic, and would be a useful device in situations that require angular motion.
This is already in layman's terms.
...this leap forward in understanding may help reveal how the smallest building blocks in nature react to form solids, liquids and gases that constitute the material world around us.However, this topic is from 2003.
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