Electrical resistance is the ability of a body to oppose the flow of electric current.
What happens is that the electric current, when established in an electrical conductor, creates a high number of electrons.
These free electrons constantly collide with each other and with the atoms of the conductor’s own metal, making movement difficult.
This is the electrical resistance caused within the conductor.
Among the main factors that can influence electrical resistance, it is worth highlighting the resistivity (measure of opposition) of the electrical conductor according to its length or cross-sectional area (when the conductor wire is thinner).
The electrical resistance of a conductor can also be classified according to the material used in its production and finish, as well as the working temperature during the passage of electric current.
Calculation of electrical resistance
To calculate the level of electrical resistance of a material, it is necessary to apply Ohm’s Second Law:
R = ρ × (L/A)
In this case, ρ represents the electrical resistivity of the conductor being tested, while R is the electrical resistance of the material itself.
It is also necessary to consider in the equation the length of the conductor, in meters, represented by L.
Another factor considered and essential to obtain the exact measurement of electrical resistance is the cross-sectional area of the conductor in square meters, represented by A.
According to Ohm’s Second Law (Ω), the calculation to obtain the electrical resistance of a given material is applied only in uniform situations of isotropic materials and that have equally continuous cross-sections.
Electrical resistance: Joule effect
The Joule effect is characterized and classified when the transformation of electrical energy into thermal energy occurs — a situation caused when some electrons cannot overcome the electrical resistance of the conductor and increase the temperature in the material.
This effect is used in showers, hair dryers, or irons, as well as incandescent lamps, heaters, and other common household appliances.
This transformation is possible thanks to the level of electrical resistance of these appliances.
In other words, they are products specially manufactured to generate the change of electric current that passes through the wire and transforms by not being able to overcome the resistivity, generating the heat that is used for various purposes.
