What is resistance?

Which Stops flow of current

‘Electricity’ is possible only due to flow of ‘electrons’. The nature or characteristic of matter ‘resisting’ this flow of electrons is known as ‘resistance’.

‘Ohm’ is the unit of resistance.

Important Points:

(a) The ‘resistance’ increases when the length of the conductor increases.

(b) The ‘resistance’ decreases when the Area of the conductor increases.

(c) When the ‘resistivity’ of the conductor is high, the resistance becomes high. The resistivity depends on the material of the conductor.

(d) The reverse characteristic of this ‘resistivity’ of a conductor is called ‘conductivity‘. Hence a conductor of higher ‘conductivity’ will be a ‘good conductor of electricity’.

(e) Likewise, a conductor of higher ‘resistivity’ will be a “bad conductor of electricity”.


R = ρL/A


 R = Resistance

L= Length of the conductor

A= Cross-sectional area of the conductor

ρ = Resistivity

S= Conductivity.

Resistance Pic 2 Electrical Gurukul
What is Resistance ?

The ‘resistivity’ of Silver is very less. The ‘resistivity’ of Copper is higher than that of Silver. The ‘resistivity’ of aluminum is higher than that of Copper.

Let me ask you an interesting question. When we increase the temperature of the conductor, what will happen to its resistance?

The ‘resistance’ will increase. Because, the atoms of the matter will vibrate severely due to such applied heat. So the path of ‘free electrons’ will be obstructed. It will affect the flow of ‘electricity’. The conductor becomes less conductivity the ‘resistance’ will increase.

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