Resistance[ class- 10]

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Resistance

Definition: It is the opposition force experienced by the flowing electrons in some substances.

This opposes the flow of electricity in a material.

The SI unit of resistance is represented by a greek symbol Ω

The resistance symbol of a resistor is given below.

Resistance Formula

The resistance formula is as follows:

Resistance = voltage drop across a resistor/ current flowing through a resistor

                         [ R = $\frac{V}{I}$]
R = resistance (Ohms, Ω)
V = voltage difference which is between the two ends of a resiistance.

RESISTANCE DIPENDS ON FOLLOWING FACTOR---

[1]- Resistance is directly proportional to the length of the material”.

 According to this law, the resistance of the material increases with the increase in the length of the material and decreases with the decrease in the length of the material.

                 [ R ∝ L ]—–------(1)

[2]-Resistance is inversely proportional to the cross-sectional area of the material”. 

According to this law, its material increases with the decrease in the cross-sectional area of the conductor and decreases with an increase in the cross-sectional area.

                     [ R ∝ 1/A ]—------(2).

[3]-Resistance depends on the nature of the material”.

According to this law, the resistance value of the material varies depending upon the type of material.

[4]-Resistance depends on its temperature”. According to this law when the temperature of a metallic conductor is increased, it’s value also increases.

From equation first and second--

               [ R = ρL/A]

where ρ is known as the resistivity constant or the coefficient of resistance.

Note-It is also known as the specific resistance of the material. Its units are Ohm-meter