The greater the resistance of the conductor, the worse it passes the electric current. The electrical resistance is indicated by the Latin letter R, and 1 ohm is taken per unit of measurement. The
inverse characteristic of the resistance of a substance is its conductivity. The higher the electrical conductivity of the material, the better it conducts the current. Insulators differ from conductors in conductivity by a huge number of times, measured by a unit with twenty-two zeros!
Resistivity. Definition and calculation
So, electrical resistance depends on the material from which the conductor is made. But there are two other important parameters — the length of the conductor and the area of its cross-section. Obviously, the longer the conductor, the longer the ions of its matter will interfere with the movement of free electrons.
But to better understand why resistance depends on the cross-sectional area, you need to make an analogy with water. Imagine two identical receptacles connected in one case by a thin tube and in the other by a thick one. A thin or thick tube will water flow faster from one vessel to another? Clearly fat.
Resistivity is the resistance of the conductor, 1 meter long and 1 mm2 cross-sectional area.
Silver and copper possess the smallest resistivity.
Thus, to calculate the electrical resistance of the conductor, we need to use the formula:
R = PL/s,
where p is resistivity, l – conductor length, S – transverse area section of the conductor.
When the temperature of the metal conductor increases, its resistance increases. This phenomenon can be explained by the fact that during the transfer of thermal energy to the body increases the intensity of movement of atoms of its matter, and this is more impeding the free current of electrons.
With the lowering of the temperature in metals, the best conditions for conducting electric current are created. There is even such a thing as superconductivity, that is, such a state of a metal conductor when its resistance is zero. At the same time, the metal atoms practically stiffen in place, absolutely without interfering with the movement of free electrons. This occurs at -273°C.