diff --git a/source/electronics/metrics.rst b/source/electronics/metrics.rst
index ae66281..209b499 100644
--- a/source/electronics/metrics.rst
+++ b/source/electronics/metrics.rst
@@ -19,3 +19,57 @@ One Newton is the force required to accelerate :math:`1Kg` of mass, at a rate of
 
 .. math::
 	[N]=kg.m.s^{-2}
+
+Joule
+^^^^^^^^^^
+It is the unit of energy.
+Its the force used to move an object when a force of one newton acts on that object in the direction of the force's motion through a distance
+of one metre.
+
+.. math::
+	[J]=[N] \times m=kg.m^2.s^{-2}
+
+Watt
+^^^^^^^
+It is the amount of Joules per seconds spent by a system.
+
+Ampere
+^^^^^^^^
+In a working circuit, electrons (Coulomb) are flowing.
+They are flowing at a certain bitrate.
+This is exactly what ampere measure.
+
+.. math::
+	[A]=\frac{C}{s}=C.s^{-1}
+
+Volt
+^^^^^^^
+To move charges in a circuit, energy is required (energy that push the charges).
+This is what volts measure.
+A volt is the amount of energy per Coulomb (remember Coulomb
+is just a constant).
+
+.. math::
+	[V]=\frac{[J]}{C}=kg.m^2.s^{-2}.C^{-1}=kg.m^2.s^{-3}.C^{-1}.s=kg.m^2.s^{-3}.A^{-1}
+
+Farad
+^^^^^^^^
+Components can hold electrons (such as capacitor).
+Farad defines the amount of Coulomb (electrons) retained by the component for each unit of voltage.
+
+.. math::
+	{[F]}=\frac{C}{[V]}=\frac{C}{kg.m^2.s^{-3}.A^{-1}}&=\frac{C}{kg.m^2.s^{-3}.C^{-1}.s}=\frac{C}{kg.m^2.s^{-2}.C^{-1}}
+
+	&=\frac{C^2}{[J]} =\frac{C^2}{[N].m} =\frac{s^2.C^2}{kg.m}
+
+	&=\frac{s^4.[A]^2}{kg.m}=m^{-2}.kg^{-1}.s^4.A^2
+
+Ohm
+^^^^^^^
+In circuits, components can resist to the current and thus reduces it.
+Ohm defines the amount of volts required at one end of the resistor to pass one ampere into it.
+
+.. math::
+	{[\Omega]}=\frac{[V]}{[A]}=\frac{kg.m^2.s^{-3}.A^{-1}}{[A]}=kg.m^2.s^{-3}.[A]^{-2}&=kg.m^2.s^{-3}.C^{-2}.s^{2}
+
+	&=kg.m^2.s^{-1}.C^{-2}