Because the ampere is the SI unit of measurement for electric current. It is defined in terms of the magnetic effect of an electric current -i.e. the force between two, parallel, current-carrying conductors, expressed in terms of newtons per metre length.
The units of power in AC reactive circuits are volt-amperes instead of watts because the voltage and current are not in phase with each other. Volt-amperes is a better indication of how much power a source such as a transformer is supplying, because watts will be less than volt-amperes due to power factor, but that energy still has to be supplied.
Current is charge per time, or coulomb per second. We simplify that as the ampere. This is accepted convention.
An amount of charge is the coulomb.
Energy per charge is joules per coulomb, also known as the volt.
Charge per second is current in coulombs per second, also known as the ampere.
Per Ohm's Law, a current of one ampere with a voltage on one volt requires a resistance of one ohm, also known as one joule-second per coulomb squared, but the term ohm is so more more convenient.
A current of one ampere across a voltage of one volt dissipates a power of one watts, also known as one joule per second.
Memorize this, and you are well on you way to understanding Electricity 101.
It is not derivable from other units. The ampere is defined in terms of a quantity of electrons flowing past a point per second. A quantity of electrons has no connection to any other unit, it requires a means of counting (or at least estimating) the number of electrons that moved.
Because the French Physicist Ampere did a lot of important research and published
a lot of new knowledge relating to electric current, so when it came time for the
scientific community to define and name new units, they immortalized his memory
by perpetuating his name as the unit of current. But of course, the whole thing was
just a twist of fate, as so many of life's developments are. Had the discoveries been
realized and published by one of his young lab assistants instead of by Professor
Ampere himself, we might be measuring electric current today with a Schwartzmeter,
a Winkelmeter, a Cohenmeter, a Chevaliermeter, etc. The mind boggles at the thought
of how close we came.
It is called Ampere. As to why, well, I guess there must be SOME standard for current.
Presumably the currently used definition was chosen because it can be reproduced with greater precision than alternate methods.
The unit of measure for voltage is volt. Ohm measures resistance.
It is expressed in Volt-Amperes not Watts.
LxW of building x 3 volt amps per sq. foot
It is common to see each of the examples used. However the technically correct way is kVA.AnswerFollowing the conventions of SI for compound units, a dot should be placed between the 'V' and the 'A', above base level: that is: kV.AThe symbols for units named in honour of individuals are always capitalised, so the symbol for volt is 'V', and the symbol for ampere is 'A'.Having said that, the symbol generally used for reactive volt amperes is var. So I suppose one could argue as neither the volt ampere or reactive volt ampere are really SI units, then they don't really have to follow SI conventions!
A transformer's capacity is rated in volt amperes(V.A). This is the product of the secondary winding's current rating and voltage rating.
NO! (the units of electric current is Amperes).
The unit of measure for voltage is volt. Ohm measures resistance.
milli volt amperes, unless it's MVA then it is Mega Volt Amperes. Such as in the use of large transformers
Divide the circuits amperage into the volt amps and you will get the voltage.
mA means milli-amperes VA means Volt-amperes
That depends on what units you use as input. If you put in current in Amps and Resistance in Ohms you will get voltage in Volts.AnswerCurrent is measured in amperes. Resistance is measured in ohms, which is a special name given to a volt per ampere. Multiply amperes by (volts per ohm), and you are left with volts.
It is expressed in Volt-Amperes not Watts.
If a device doesn't give its power rating in kVA (or VA), then it can be calculated pretty easily: (volt-amperes) VA = V (voltage) x A (maximum amperage) (kilovolt-amperes) kVA = VA (volt-amperes) / 1000
Mega volt amperes
Amps or amperes
The symbol, kV.A (not 'KVA'!) represents 'kilovolt amperes', and is a multiple of the volt ampere, used to measure the apparent power of an a.c. circuit, that is the product of supply voltage and load current.Apparent power (expressed in volt amperes) is the vectorial sum of a load's true power (expressed in watts) and its reactive power (expressed in reactive volt amperes).
240 amps AC