Russo Marco 5 a E

 Ohm’s Law is a Math formula that establishes the relation between the three main classes of electricity: the resistance, the current and the voltage.  There are three different ways that are used to represent Ohm’s law.  R is the resistance which is represented by the omega symbol. This is the ability of a material to restrict the flow of electrons.  All materials have a resistance. They can obstruct the flow of electrons or allow them to flow freely.  In the international system the unit of measurement of the resistance is the ohm.

 V is Voltage which is the difference in electrical potential between two points.  The difference of potential among the terminals of a circuit is the same as the result of the resistance of this circuit by the electric current intensity that passes by that circuit. Mathematically we have:  I is the current which is the rate of the flow of electrons in a circuit. Measured in amperes. This is a measurement recording in one second how many electrons are passing a specific point. Mathematically we have:  For the first Ohm’s law, the characteristic curve of a metal is a straight line passing through the origin of the axes.

 For the second ohm’s law the resistance depends on the nature and size of the conductor.  He clearly defined the electric resistance of a conductor. He himself demonstrated that the resistance of a conductor is directly proportional to its length and inversely proportional to the area of its transversal section.  ρ = resistivity, depends on the material of the conductor and its temperature. ℓ = width of the conductor. A = area of the transversal section.  With a cylindrical conductor of length L and transversal section A, we will see that its electric resistance is bigger when the length L is bigger and the section A is smaller, and the electric resistance will be smaller when the length L is smaller and the section A is bigger, and also depending on the material the conductor is constituted through a coefficient nominated resistivity (ρ).

 There is one more important variable which is power. This is expressed in watts or wattage. It is the process in which electrical current releases heat. There are three different ways to calculate wattage:  The electric current is a result of free electron movement. When the electric current circulates the particles that are in movement end up hitting the other parts of the conductor that are in rest, causing a kinetic energy variation that will generate a heating effect. This heating effect is named Joule’s effect. Mathematically we have:  Q = (I)²(R)(t) Where: I = current intensity R = conductor resistance t = time that the current travels the conductor