Think of water flowing through a pipe: if you double the restriction or narrowing (resistance) of the pipe while keeping the water pressure (voltage) constant, the flow rate (current) of water will be cut in half.

Ohm's Law states that current ($I$) is directly proportional to the voltage ($V$) and inversely proportional to the resistance ($R$), expressed as $I = \frac{V}{R}$. If the resistance $R$ is doubled to $2R$, the new current becomes $I' = \frac{V}{2R} = \frac{1}{2} I$, which is exactly half of the initial current.

In competitive exams like RRBJE, questions testing proportional reasoning with Ohm's Law ($I \propto \frac{1}{R}$) are common and can be solved quickly without full calculation.