Historically, prior to 1820, electricity and magnetism were thought to be separate entities of nature. On April 21, 1820, Hans Christian Oersted, a Danish physicist, conducted a lecture demonstration on electricity in Copenhagen, Denmark. In his demonstration, he set up a wire conductor tied to posts. There was also a compass somewhere near his experiment. Then he let electric current flow through the wire. It was then at this moment that he accidentally observed that the current flowing through the wire deflected the compass needle. He repeated it to make sure that the current flowing through the wire was really the cause of the deflection. And it was really the cause. It was then a remarkable discovery. It showed for the first time that electricity and magnetism were in fact related to each other.
It was then established that a current-carrying conductor produces a force around it in circular form, which has been called magnetic field. It was this magnetic field around the wire that caused the compass needle to deflect.
News of the discovery spread like wildfire. It reached France quickly. Andre Marie Ampere, the French scientist and mathematician, who founded the science of electrodynamics, quickly conducted experiments to investigate the electric-magnetic phenomenon further. In his experiments, he discovered some behaviors of two wires both carrying electric current. The results of his experiments would be presented here. They could not be encountered in the discussion on electromagnetism in standard physics books. But this behavior of electromagnetism would seem to be important for a deeper understanding of this force in the universe.
Ampere’s experiment is composed of two test wires. One is the main wire that carries electric current and the other is a test wire also carrying electric current. Pursuing Oersted’s experiment further, Ampere investigated this phenomenon. He sought to find out what happens if another conductor (wire) carrying electric current is to be placed near the first conductor. So he set up a shorter test wire near the main wire to see what would happen. And here is the result of Ampere’s investigation that would seem to have been neglected or perhaps deliberately concealed.
“Ampère discovered that the force exerted on the test wire is directly proportional to its length. He also made the following observations. 1] If the current in the test wire (i.e., the test current) flows parallel to the current in the central wire, then the two wires attract one another. 2] If the current in the test wire is reversed, then the two wires repel one another. 3] If the test current points radially towards the central wire (and the current in the central wire flows upward), then the test wire is subject to a downward force. 4] If the test current is reversed, then the force is upward. 5] If the test current is rotated in a single plane, so that it starts parallel to the central current and ends up pointing radially towards it, then the force on the test wire is of constant magnitude and is always at right angles to the test current. 6] If the test current is parallel to a magnetic loop, then there is no force exerted on the test wire. 7] If the test current is rotated in a single plane, so that it starts parallel to the central current, and ends up pointing along a magnetic loop, then the magnitude of the force on the test wire attenuates like cos. In this context, cos represents the angle through which the current is turned, where cos -- 0 corresponds to the test current being parallel to the central current. The direction of the force remains consistently at right angles to the test current. 8] Finally, Ampere was able to establish that the attractive force between two parallel current carrying wires is proportional to the product of the two currents and falls off like one over the perpendicular distance between the wires.”
I would like to point out what I consider as an important thing in this experiment. It is the fact that what is called magnetic field extends from the wire to space. In other words, it fills space and it can influence another magnetic field nearby that also fills space (that of the shorter test wire in Ampere’s experiment). And, again, there are specific behaviors of the interaction of the two current-carrying conductors with their respective magnetic fields around each of them, as listed by Ampere from his experiment.
The importance of this experiment for me lies in the fact that it could give a clue as to whether this might be the force that fills up space, such as the space in the solar system and even beyond, rather than what is called gravity, a seeming hypothetical force. There is a story we learned in high school that one time Isaac Newton was struck by a falling apple. It sparked his fertile mind, thinking that there must be a force pulling the apple downward. To cut the long story short, the concept of gravitational force was conceived and since the publication of Newton’s Principia in 1687, it has been the accepted theory. But one thing to note here is that the phenomenon of magnetism (or, say, electromagnetism) was still in a seminal stage at the time of Newton. Thus, it could be that the so-called gravitational force could be seen as a hypothetical force, presumed to be the force governing the solar system and/or the entire universe, but, in reality, it is rather the magnetic field filling up vast space.
It could be surmised, then, as to which is more probable: the presumed (so hypothetical) gravitational force conceived by Newton or the experimentally proven behavior of magnetic fields in Ampere’s experiment. It is one food for thought.