On which of the following factors does the resistance of a conductor depend?

Use the data in the table to answer the following: Which among iron and mercury is a better conductor?
< p style="text-align:center"> < span style="font-size:14px"> Electrical resistivity of some substances at $20\,^oC$

Material	Resistivity $(\Omega \,m)$
Iron	$10.0 \times 10^{-8}$
Mercury	$94.0 \times 10^{-8}$

What is the symbol used to denote the unit of resistance,ohm?

State Ohm's law. How can it be verified experimentally? Does it hold good under all conditions? Comment.

What is the resistance of an ideal voltmeter?

$A$ student carries out an experiment and plots the $V-I$ graph of three samples of nichrome wire with resistances $R_1, R_2$ and $R_3$ respectively (Figure). Which of the following is true?