If the length of a wire is stretched to double its original length while keeping its volume constant, its new resistance will be: MCQ with Answer and Explanation

Resistance R = rhoL/A. If the wire is stretched so length becomes L' = 2L, the volume (V = AL) must remain constant. Therefore, the new area A' must be A/2 to maintain V. The new resistance R' = rho(2L)/(A/2) = 4 * (rhoL/A) = 4R. Stretching a wire to double its length increases its resistance strictly by a factor of 4. This is a classic trap question compared to merely 'changing the wire'.