The resistance of a wire is R Ω. If it is melted and stretched so that its original length is increased eight times, its new resistance will be:
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The resistance of a wire is R Ω. If it is melted and stretched so that its original length is increased eight times, its new resistance will be:

G1 Physics · Accepted Answer

Step 1: For fixed mass/volume A·l = constant, so A′ = A/8 if l′ = 8l. Step 2: R′ = ρl′/A′ = ρ(8l)/(A/8) = 64R. Step 3: Compare original scan: wording appears to specify length stretched to n times; correct general law is R′ = n²R.