The resistance of wire is 20ohm. Find the resistance of the wire when it is stretched so that the length increases by 10%. (please explain it in detail with ans)
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The wire’s length is stretched to twice its length I.e. area of cross section decreases or becomes half, since volume remains the same.
R= (row*L)/A
row - specific resistance
L - length of wire
A- Area of cross section wire
Ur condition
New R= (row*2L)/(new A)
new A = old A/2 as per below derivation
Hence new R = (row*2L)/(A/2)
New R = 4*( (row*L)/A))=4*old R
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For area and length relation
Volume of cylinder =pi*r*r*L=A*L
r - radius of flat surface or tip of wire.
A=area of cross section
A=pi*r*r
I hope this helps!
Feel free to correct the mistakes :)
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