Question

What is ohm's law? Explain how it is used to define the unit of resistance.

Answer 1

According to Ohm's Law, the flow of current through a conductor is directly proportional to the potential difference applied at its ends provided that temperature and physical conditions are constant.
$V\propto I$

$\Rightarrow V=IR$

where R is the constant of proportionality, which is called resistance.
Unit of potential difference is volt (V) and that of current is ampere (A).

Hence from relation V = IR,

R = V/I

The unit of resistance is the ohm(Ω).

If V=1 Volt and I=1 Ampere , then R = (1V)/1A) = 1 Ω.

Thus, 1 Ohm is the resistance of a conductor such that when a potential difference of 1 Volt is applied to its ends and a current of 1 Ampere flows through it.