A wire has a resistance R. It is stretched uniformly so that its lengt…

Question

A wire has a resistance R. It is stretched uniformly so that its length becomes 2L. The new resistance is

Accepted Answer

C. {'text': '4R', 'label': 'C'}

1. Stretching keeps volume V = A × L constant; if L doubles, A halves.
2. Original R = ρ L / A. New length L' = 2L, new area A' = A/2.
3. New R' = ρ (2L) / (A/2) = 4 ρ L / A = 4R.
4. So on doubling the length by stretching, resistance becomes four times.
_Source: NCERT Class 12 Physics, Ch 3 "Current Electricity", §3.4_

Answer

{'text': 'R/4', 'label': 'A'}

Answer

{'text': 'R/2', 'label': 'B'}

Answer

{'text': '2R', 'label': 'D'}