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Entanglement
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What's the original definition of Ohm, ampere, volt and coulomb,
And which unit was defined according to the other ??!
And which unit was defined according to the other ??!
Why didn't ampère suppose that 1 ampere is the current the passes through two wire held 1m apart, and a force of 1 Newton is exerted on them why did he choose 2 x 10 to the power -6??jtbell said:The fundamental one is the ampere:
http://physics.nist.gov/cuu/Units/ampere.html
The others are derived from it:
1 coulomb = 1 ampere * 1 second
1 volt = 1 joule / 1 coulomb
1 ohm = 1 volt / 1 ampere
I just wanted to sort how these unitswere originatedjtbell said:M. Ampère did not define the unit. It is merely named after him, in his honor.
The history of electromagnetic units is a long and complicated one. Several different sets of such units have been used in the past, and to some extent even today. My head aches whenever I try to sort them out.
http://info.ee.surrey.ac.uk/Workshop/advice/coils/unit_systems/
At least the ampere will soon be redefined in terms of elemental charge instead of the other way around.ElmorshedyDr said:I think volt is originally derived from something else because it's not logical that both ohm and volt are derived from ampere and fitted in the equation V=RI
The present definition of the ampere, however, is vulnerable to drift and instability. This is not sufficient to meet the accuracy needs of present and certainly future electrical measurement. The highest global measurement authority, the Conférence Générale des Poids et Mesures, has proposed that the ampere be redefined in terms of the electron charge.
What about ampere ??Meir Achuz said:Yes, a meaningless constant.
But SI.made the equations more complicated as it induced constants to equations that never needed a constantUltrafastPED said:All of the constants are scaling factors ... if the definitions of the units are changed, the scaling factors change.
They are about as meaningful as 12 inchs = 1 foot.
That is, they both measure distance, and an engineer has to get it right (or else things don't work), but mathematically they can be adjusted to whatever you like ... as long as your final answer is given in some appropriate units.
So theoreticians like to set c=1 so that the equations are simpler; this means that time is now measured in "light seconds". Very nice if you like simple equations, but not convenient otherwise.
Being a physicist-engineer, I prefer the SI units, but I know people who prefer every other possible combination. Yuck.
ElmorshedyDr said:But SI.made the equations more complicated as it induced constants to equations that never needed a constant
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
The German scientist Georg Ohm is credited with discovering Ohm's Law in the early 19th century.
An ampere is a unit of electric current, defined as one coulomb of charge per second.
A volt is a unit of electrical potential or electromotive force. It is defined as the potential difference across a conductor when a current of one ampere dissipates one watt of power.
A coulomb is a unit of electric charge, equivalent to the charge of approximately 6.24 x 10^18 electrons.