The characteristics of dipoles
Fondamental : Conventions generator and receptor
Fondamental : Characteristic of a dipole
Fondamental : Characteristic ohmic conductors, Ohm's law
Ohm's Law (see also "Local Ohm's law") :
is the conductor resistance (expressed in ohm, )
Where is the conductance of the conductor (expressed in Siemens, ).
Associations of ohmic conductors :
In series :
The resistors are added :
In parallel (in derivation) :
Conductances are added :
JAVA animation (of JJ.Rousseau, University of Le Mans) on the color code of resistance :
Fondamental : Characteristics of generator (linear active dipole)
The characteristic of a generator (generator convention) is given in the following figure.
It is a linear active dipole, whose characteristic can be modeled as :
: open circuit voltage ( ), measured with a voltmeter.
: Short circuit current ( ), measured with an ammeter.
We denote :
The linear active dipole is thus equivalent to the following two elements in series :
An ideal emf generator voltage denoted (equal to open circuit voltage at the terminals of the dipole).
Ohmic conductor resistance (internal resistance of the active dipole).
This modeling of the active dipole is called "Thevenin's modeling"
Norton's modeling :
The linear active dipole is equivalent to the following two elements placed in parallel :
An ideal current generator of electromotive current (equal to the short-circuit current of the active dipole),
in parallel with :
ohmic conductor resistance (internal resistance of the active dipole).
This modeling of the active dipole is called "Norton's modeling".
One passes from the representation of the Thevenin to Norton using the following relationships :