Question

Question 24
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 (also known as resistivity, specific electrical resistance, or volume resistivity) is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge. Resistivity is commonly represented by the Greek letter $\rho$ (rho). The SI unit of electrical resistivity is ohm metre ($\Omega$ m) although other units like ohm centimetre ($\Omega$ cm) are also in use.
Many resistors and conductors have a uniform cross section with a uniform flow of electric current, and are made of one material. In this case, the electrical resistivity $\rho$ is defined as:
$\rho =R\frac{A}{l},$
where,
R is the electrical resistance of the material
l is the length of the piece of material
A is the cross - sectional area of the specimen
If the length is doubled, the resistance of the wire will also become double. Due to which the current in the ammeter reading drops to half.