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?

Answers (1)

Electrical Resistivity (or resistivity) is a property of the material of a conductor is the resistance offered by the conductor of unit length with the unit cross-sectional area.

            
ho = fracRAl    Here R is resistance

                                            A is the area of cross-section

                                            l is the length of wire

                                           
ho is the resistivity

Unit of eginalign* 
ho &= frac	extOhm metre^2	extmetre \ & = 	extOhm metreendalign*

SI unit of restiivity is Omega  m  (	extOhm Metre)

We know that     

                        R = frac
ho lA

                        R propto l

If the length of the wire is doubled then the resistance of the conductor also doubles. So, the current is reduced to half

                        Ipropto frac1R

	herefore Ammetre reading = frac100mA2 = 50mA

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