It is the first law
taught in electrotherapy.
The tension U (expressed in Volts V) which exists at
the boundaries of a resistance R (expressed in ohms W) is directly proportional to
intensity I (in Amps A) which crosses this
resistance.
The tension V is expressed by the product of
resistance R and current I.
and the derived
formula ;
The current I which crosses a resistance R is
directly proportional to the tension U applied at the
boundaries of resistance.
Current I is expressed by the ratio of the tension U
and resistance R.
The importance to
be given to these two formulas is the close friend
connection of the current and the tension. They do
not exist one without the other.
These formulas
present significant limitations.
It is necessary, indeed, that R is purely resistive.
In electrotherapy, it is almost never the case
Moreover, these formulas are indicated and valid only
for D.C. current, less used in neurostimulation.
