Here’s an interesting news item from the National Institute of Standards and Technology (NIST) that discusses a proposal for changing the way we define several basic quantities, including the Ampere.
According to this article, the Ampere is
now defined in terms of a current that, if maintained in two straight parallel conductors of specific sizes and positions, would produce a certain amount of [magnetic] force between the conductors.
As you can imagine, this would be difficult to do accurately, as the accuracy of the measurement would depend on how accurately you could measure the position of the conductors, how accurately you could maintain a constant current, and how accurately you could measure the force between the two conductors.
Instead, researchers propose
linking the ampere to a specific value for the elementary charge, which is the electric charge carried by a single proton, a particle with a positive charge in an atomic nucleus. The ampere might be defined, for example, as the electric current in the direction of the flow of a certain number of elementary charges per second.
It seems to me that there would still be plenty of room for error in measuring an Ampere accurately. One would have to be able to accurately count the number of protons flowing in the conductor over a period of time, although that might be easier than measuring a small magnetic force.
Fortunately, for most radio amateur radio applications, hooking up that $10 multimeter to our gear will give us a reading that’s accurate enough for our purposes.
Leave a Reply