What should be the answer?

If length of a conducting wire is increased by $0.1$ %, the the resistance will increase by how much percentage?

A. $2$ %

B. $0.2$ %

C. $1$ %

D. $0.1$ %

#ElectricityAndMagnetism

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Comments

@Calvin Lin ,@Chung Kevin ,@Nihar Mahajan , @Mehul Arora ....plz help!!!

Sahba Hasan - 5 years, 10 months ago

First, Thanks for mentioning me, Though I don't deserve that honour :)

Then, When a wire is stretched by x%, Then resistance will increase by 2x%. but this is applicable only x<10 (I don't know why, though)

Thus the answer should be 0.2%

Mehul Arora - 5 years, 10 months ago

Thanks...you really helped me!

Sahba Hasan - 5 years, 10 months ago

@Sahba Hasan – Always welcome brother! :)

Mehul Arora - 5 years, 10 months ago

@Mehul Arora – Well....i am a girl. ;)

Sahba Hasan - 5 years, 10 months ago

@Sahba Hasan – Sorry, Sister* :P

Mehul Arora - 5 years, 10 months ago

Answer should be 0.2%.

Anibrata Bhattacharya - 5 years, 10 months ago

Resistance of a wire depends inversely on area of cross section and directly on length of wire. But, since volume of wire remains constant, an increase in length causes a decrease in area. Dividing the new length by new area obtained, we get the new resistance.Subtract 1 from this and then multiply by 100.This will give you the %.The calculation is not long, but it involves big numbers like 1000 and 1001(even their squares!).Use difference of 2 squares rule(HINT).Calculate, and u will get the answer very close to 0.2(actually, 0.2001). Sorry, couldn't show the calculation here!

Anibrata Bhattacharya - 5 years, 10 months ago

Thanks for your help.

Sahba Hasan - 5 years, 10 months ago

You are welcome!

Anibrata Bhattacharya - 5 years, 10 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$