Physicshard · Past Paper
A wire of resistance R is stretched to double its original length while keeping volume constant. What is its new resistance?
A2R
B4R
CR/2
DR/4
✓ Correct Answer: B — 4R
If length L is doubled and volume (A*L) is constant, area A must become half. R = ρ(2L)/(A/2) = 4 * ρL/A = 4R.
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