If a copper wire is stretched to make it 0.1% longer. The percentage change in its resistance is
Step 1: Given data and formula used
Resistance, R=ρlA
where ρ is resistivity, l is original length and A is cross sectional area of wire.
Multiplying and dividing by length l
R=ρl2A×l=ρl2V
Step 2: Calculation of Percentage change in resistance,
%R=R′−RR
R′=ρ(1.001l2)V ∵(New length, l′=l+0.1100l=1.001l)
R=ρl2V
⇒ %R=ρ(1.001l2)V′−ρl2Vρl2V×100
%R=0.2001%
Hence resistance increase by 0.2%.
The correct option is B 0.2% increase