The Electric current- amazing stuff about the topic

The document presents interesting facts, stupefying questions, etc. about electric current.

1. In the name of JAMES CLARK MAXWELL … The Electric Current Naini Diwan Natural sciences

2. What is electric current? The #Wikipedia definition is that: “Amperage, or electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space .” Now, a simple but wrong interpretation of this statement is tha t, “Electric current is charge that is moving past a given point (or area) over time.” But everything is made up of atoms. A baseball is made of charges. So if I throw a baseball, is it electric current? It actually refers to the net charge moving past a given point (or area) over time . If there is current in a copper wire, for instance, it means some non zero charge has passed through its cross section.

3. Just some bonus deets from a great book… In the calculus of quaternions, invented by Hamilton, quantities were first divided into scalars and vectors. Stress & strain are related to directions in space but are not vectors. These require for their definition 9 numerical specifications. They’re expressed in the language of quaternions. The modern picture is: rank-n tensor will accept n vectors and return a scalar value. Electric current is a rank-0 tensor. Elasticity stress and strain tensors fall under rank-2. [For more about tensors, I have a nice document]

4. Why me so special? Take it this way.. Why is electric current a fundamental quantity rather than electric charge? Afterall, look at what Griffiths says

5. Measuring the current with instruments such as an ammeter is easier than counting the number of charges flowing in the circuit. Or Fundamental quantities are those that are unique and do not depend on any other quantity. But charge does, Q=I*t Or Historically, electric current was measured accurately before electric charge.??? Dexler in the year 1884 invented the ammeter. Is that because… Although in 1600, William Gilbert invented the first electroscope with a pivoted needle called versorium . But an electroscope acts as an indicator of electric charge and not a measuring device. Thus, calibrated electrometer with a more robust aluminum indicator was invented by Ferdinand Braun and first described in 1887 (after ammeter).

6. Theoretically, any one of electric current, potential difference, electrical resistance, or electrical charge could have provided the base unit, with the remaining units then being defined by the laws of physics. In the event, the unit of electric current was chosen for SI. It was perhaps the one easiest to define in terms of measurements one could do—that is, the definition is based on forces felt by parallel current carrying wires .

7. And yet another one: Notice again what Griffiths says… Tell me if you’ve never heard about something called relative mass. So, you can’t say that it’s impossible for a charge to depend on velocity of the body which possesses it (don’t forget that charge can’t exist without mass). Bear with me… But there’s another perspective of looking at it: Let’s illustrate the issue with a capacitor. If you connect a capacitor to a battery, current will flow. But if you look at the part of the circuit inside the capacitor, no actual charged particles cross this gap. The current exists by virtue of an increasing electric field across the dieletric , not charge flow. In this sense, current is a more fundamental concept than moving charges. Magnetic field at a point due to moving charge depends on observer. But due to a current carrying wire, magnetic field at a point doesn’t depend on the observer. Because with respect to him, motion of positive charge is also affected.

8. This is what it means…

9. In the 1880’s, there was a “war of currents” between Nikola Tesla and Thomas Edison. Tesla helped invent AC current and Edison helped invent DC current, and both wanted their currents to be popularized. AC won the battle because it’s safer and can be used over longer distances.

10. That’s all Folks