A wire of resistance 5 is drawn out so that its length is increased by twice its original length, its new resistance is

Step-by-step solution

Resistance of a wire is given by R= L A where, = resistivity, L= length of the wire A= area of cross- section of the wire Equating initial and finial volumes of the wire, we can write A L=A^ L^ =A^ (2 L) A^ = A 2 R^ R = L^ / A^ L / A = ( L^ L ) ( A A^ )= ( 2 L L ) ( A A / 2 )=4 R^ =4 R=4(5)=20