What is electrical resistance $(R)$? On which factors does the resistance value depend?

(N/A) Electrical resistance is the property of a conductor to oppose the flow of electric charge through it.
From Ohm's law,$R = \frac{V}{I}$. Its $SI$ unit is $\frac{\text{Volt}}{\text{Ampere}} = \text{ohm} (\Omega)$. Its dimensional formula is $[M^1 L^2 T^{-3} A^{-2}]$.
Resistance depends on the following factors:
$1$. Length of the conductor $(l)$: $R \propto l$
$2$. Cross-sectional area of the conductor $(A)$: $R \propto \frac{1}{A}$
$3$. Nature of the material (resistivity,$\rho$)
$4$. Temperature of the conductor
Consider a conductor with length $l$ and area $A$ as shown in Figure $(a)$.
Two such similar rectangular blocks are shown in Figure $(b)$. Here,the total length of the combination is $2l$.
The current flowing through the combination of blocks is equal to the current flowing through each individual block. Hence,the potential difference across each block is $V$. Therefore,the total potential difference across the combination is $2V$. Let the resistance of the combination be $R_C$. By Ohm's law:
$R_C = \frac{2V}{I} = 2R$
Since $\frac{V}{I} = R$ is the resistance of each block,we see that the resistance of the conductor is proportional to its length $(R \propto l)$.