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  • What is electrical resistivity? Derive its SI unit. In a series of an electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 100 mA. If the length of the wire is doubled, how will the current in the circuit change? Justi

What is electrical resistivity? Derive its SI unit. In a series of an electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 100 mA. If the length of the wire is doubled, how will the current in the circuit change? Justify your answer.

 

 

 

 
 
 
 
 

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.

            \rho = \frac{RA}{l}    Here R is resistance

                                            A is the area of cross-section

                                            l is the length of wire

                                           \rho is the resistivity

Unit of \begin{align*} \rho &= \frac{\text{Ohm metre}^2}{\text{metre}} \\ & = \text{Ohm metre}\end{align*}

SI unit of restiivity is \Omega \ m \ (\text{Ohm Metre})

We know that     

                        R = \frac{\rho l}{A}

                        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

                        I\propto \frac{1}{R}

\therefore Ammetre reading = \frac{100mA}{2} = 50mA

 

Posted by

Sumit Saini

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