Length increases, Diameter decreases,then resistance?

Electricity and Magnetism Level 3

The length of a given cylindrical wire is increased by 100% . Due to the consequent, there is d e c r e a s e \color{#456461}{decrease} in diameter.

The change in the r e s i s t a n c e \color{#0C6AC7}{resistance} of the wire will be

50% 200% No change 400% 100% 300%

Akhil Bansal by Akhil Bansal , 22, India

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2 solutions

Saurabh Meena
Aug 18, 2015

sol sol

3 Helpful 0 Interesting 0 Brilliant 0 Confused
Rwit Panda
Sep 25, 2015

We have the length doubled but the total volume of the part of the error remains same. So (cross sectional area)*(length) is constant. As length is doubled so area is halved. Now, as resistance is proportional to L/A, so new resistance is 2L/A/2 = 4L/A. So it is increased by 300%. Ola!!!!

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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