A wire of length I and area of aou-aection A wu dnwn into a wire of double Its length by melting orignial resistivity and resistance were rho and R and resistance ?

A wire of length I and area of aou-aection A wu dnwn into a wire of do

1.	A wire of length I and area of aou-aection A wu dnwn into a wire of double Its length by melting orignial resistivity and resistance were rho and R and resistance ?
Answer» Solution :We know R `= rho (I)/(A)` When a wire is doubled by melting, its length would become DOUBLE and area of cross-section would be HALVED i.e., length of wire =2I and area of crose section `=(A)/(2)` . Thus we have `R_(1) =(2rhol)/((A)/(2))=(4rhol)/(A)` where `R_(1)` is the NEW resistance . Therefore, the new resistance of the wire is 4 R. As resistivity of a material is the characteristic of a given material, hence it remains unchanged.