Physics Problem

[jmcoreymv]

Hey Ive been working on my physics homework and Ive got it mostly done. Theres this one problem which i just cant figure out how to do it so maybe someone can give me some pointers.

"A thin rod of length l and uniform charge per unit length (lambda) lies along the x axis. (A) show that the electric field at P, a distance y from the rod, along the perpendicular bisector has no x component and is given by E=2(Ke)(lambda)(sin theta not)/y. (B) using your result to part (a), show that the field of a rod of inifinite length is E=2(Ke)(lambda)/y. (Hint: first calculate the field at P due to an element of length dx, whcih has a charge (lambda) dx. Then change variables from x to theta, using the facts that x=y tan theta and dx=y sec^2 theta and integrate over theta."

Any help is appreciated.

 

[jmcoreymv]

Bump!

 

[jmcoreymv]

No one knows......

 

[saltedeggman]

Electricity and Magnetism...well...i need a picture to better picture it

 

[KMurphy]

It's not too hard, but I'm too drunk to read the second half of my physics book to help you out right now. I'll try tomorrow if nobody else steps up. The grim reapers are coming to my employment location next week to give people their walking papers and I'm the most junior employee in our section. I've been job hunting like no tomorrow this weekend and have finally submitted enough resumes and cover letters to ease my tension for the night.

What book are you using, mine was Serway's Fourth Edition.

 

[jmcoreymv]

Looks like my book is Serways fifth edition, in this one its chapter 23 problem 35

 

[jmcoreymv]

Ahh.....ill never figure this out

 

[TuxDave]

Originally posted by: jmcoreymv
Hey Ive been working on my physics homework and Ive got it mostly done. Theres this one problem which i just cant figure out how to do it so maybe someone can give me some pointers.

"A thin rod of length l and uniform charge per unit length (lambda) lies along the x axis. (A) show that the electric field at P, a distance y from the rod, along the perpendicular bisector has no x component and is given by E=2(Ke)(lambda)(sin theta not)/y. (B) using your result to part (a), show that the field of a rod of inifinite length is E=2(Ke)(lambda)/y. (Hint: first calculate the field at P due to an element of length dx, whcih has a charge (lambda) dx. Then change variables from x to theta, using the facts that x=y tan theta and dx=y sec^2 theta and integrate over theta."

Any help is appreciated.

You can get part A) in two ways. One, you can claim symmetry. That the amount of charge on one side of the x-axis is equal the the other side of the x-axis (because you're at the perpendicular bisector... so you're in the middle). Otherwise, you must show the integral, and due to symmetry, the integral will evaluate to zero.

As for the infinite rod length thing, I would cheat and just use Gauss's law where your gaussian surface would be a cylinder surrounding the rod.

 

[Darien]

I did this rather quickly, so hopefully there's no errors.



Should help you out a bit



link



EDIT:...wow...my writing sucks...