Question

What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 5 A. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?

Answer 1

Electrical resistivity is the inherent property of the resistor because of which it opposes the flow of electric current. It depends only on the nature and temperature of the resistor.

Resistance varies as directly proportional with the length. When the length is doubled then resistance also become double. Current is inversely proportional to resistance according to Ohm's law. If the resistance becomes double then current will become half i.e 5 A to 2.5 A.

This is why the reading of the ammeter decreases to half.