Ohm’s law states that the current density \( \overrightarrow{j} \) is proportional to the electric field \( \overrightarrow{E} \), with the conductivity \( \sigma \) as the constant of proportionality: \[ \overrightarrow{j} = \sigma \overrightarrow{E} \] This expresses the relationship between the electric field and current density inside a conductor.
Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R):
Assertion (A): In an insulated container, a gas is adiabatically shrunk to half of its initial volume. The temperature of the gas decreases.
Reason (R): Free expansion of an ideal gas is an irreversible and an adiabatic process.
In the light of the above statements, choose the correct answer from the options given below: