According to wikipedia the only SI fundamental unit for Matters Electrickal is the ampere. Don't you at least need the ohm to derive anything? How would you make volts from only amps?
Perhaps I misunderstand the meaning of "fundamental unit".
Ultimately, all SI units must be traceable to Mass, Length and Time. The current definition of the Ampere is:
The constant current which will produce an attractive force of 2 × 10–7 newtons per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum.
As the Newton is a measure of force, and therefore given by Mass * Acceleration (second order speed, distance / time), the definition ultimately reduces to a form that is derived from only Mass, Length and Time.
All other electrical units may be derived from this, as noted in other answers.
Volt is defined as Work done for unit charge. Charge can be derived from product of current and time. So volt can be expressed in terms of mass, distance, time and current.
Now for ohms, it can be defined as the ratio of voltage and current. So it can also be expressed in terms of mass, distance, time and current.
So with just a unit for current combined with other fundamental quantities, we can define all the other electrical quantities.
The Ampere is actually not a fundamental unit. It is Coulombs/second, with Coulombs and seconds being the fundamental units. Other common electrical units can be derived from the non-electrical fundamental units and the Coulomb. For example, a Volt is a Joule/Coulomb, or expressed in fundamental units is a Netwon-meter/Coulomb. A Ohm is a Newton-meter-second / Coulomb^2. You can continue on and derive Farads, Henries, etc, similarly.
I noticed that I used Netwons above, which is also not a fundamental unit. A Newton is a Kg-m/s^2. A Volt expressed in terms of fundamental units (Kilogram, meter, second, and Coulomb) is therefore Kg-meter^2/second^2-Coulomb.
The correct term is 'base', not 'fundamental', unit. In SI, there are seven base units, including the ampere. The coulomb is a 'derived' unit, defined in terms of the ampere and the second.
The ampere was chosen as a base unit, because it is easily measured, whereas the coulomb is not.
Interestingly, there is a move afoot to redefine the ampere (which will remain a base unit) in terms of the fundamental charge on an electron (not in terms of coulombs). However, the number of decimal places has yet to be set.
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