Sun June 17, 2012 By: Kiran Kumar

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?

Expert Reply
Sun June 17, 2012
Electrical resistivity is the property of the material independent of the geometry of conductor. It is basically resistance for a given area of cross-section of conductor per unit length.
When length of wire is doubled, the resistance is also doubled, because resistance is directly proportional to length of wire. Hence according to ohms law for a given potential difference, the current reduces to half.
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