image
Physics Forums Logo
image
image
* Register * Upgrade Blogs Library Staff Rules Mark Forums Read
image
image   image
image

Go Back   Physics Forums > Physics > General Physics


Notices

Reply

image What would a voltmeter read if it were connected between the surface of the cylinder Share It Thread Tools Search this Thread image
Old Feb10-10, 07:54 AM                  #1
kimm

kimm is Offline:
Posts: 7
What would a voltmeter read if it were connected between the surface of the cylinder

.A very long insulating cylindrical shell of radius 6.00 cm carries charge of linear density 8.90*10^-6 C/m spread uniformly over its outer surface.
*What would a voltmeter read if it were connected between the surface of the cylinder and a point 4.70 above the surface. and What would a voltmeter read if it were connected between the surface and a point 1.00 from the central axis of the cylinder?

I started with this equation
delta V= ( lemda/ 2pi epslion) (ln(rb/ra))
  Reply With Quote
Old Feb10-10, 08:18 AM       Last edited by uart; Feb10-10 at 08:26 AM..            #2
uart

uart is Offline:
Posts: 1,502
Re: What would a voltmeter read if it were connected between the surface of the cylin

distance units? 4.7 ???, 1.0 ???

Originally Posted by kimm View Post
I started with this equation
delta V= ( lemda/ 2pi epslion) (ln(rb/ra))
Ok so presumably you've substituted your numbers into this formula and got an answer. What exactly is the problem?
  Reply With Quote
Old Feb10-10, 08:21 AM       Last edited by uart; Feb10-10 at 08:26 AM..            #3
uart

uart is Offline:
Posts: 1,502
Re: What would a voltmeter read if it were connected between the surface of the cylin

BTW. Assuming the above are both in units of cm, then your equation is valid for the first measurement but not for the second one. Do you know why?
  Reply With Quote
Old Feb10-10, 08:47 AM                  #4
kimm

kimm is Offline:
Posts: 7
Re: What would a voltmeter read if it were connected between the surface of the cylin

i did like this
(8.90* 10^-6/ 2 pi 8.85*10^-12)ln (4.5/6)
i got -39084.73
but the answer was wrong
what i am not sure about is ln ra and ln rb
i substituted ra cm and rb 4.5 cm
  Reply With Quote
Old Feb10-10, 08:48 AM                  #5
kimm

kimm is Offline:
Posts: 7
Re: What would a voltmeter read if it were connected between the surface of the cylin

ra is 6 cm
  Reply With Quote
Old Feb10-10, 09:46 AM                  #6
uart

uart is Offline:
Posts: 1,502
Re: What would a voltmeter read if it were connected between the surface of the cylin

Originally Posted by kimm View Post
i did like this
(8.90* 10^-6/ 2 pi 8.85*10^-12)ln (4.5/6)
i got -39084.73
but the answer was wrong
what i am not sure about is ln ra and ln rb
i substituted ra cm and rb 4.5 cm
Well for one I don't even get that answer when I use your numbers. Double check your calculator usage.

In any case the numbers you're using are not correct. I think you should be using Ra = 6cm and Rb = 10.7 cm.

Are the distances of 4.7 and 1.0 methioned in you question in cm ????????
  Reply With Quote
Old Feb10-10, 09:48 AM                  #7
uart

uart is Offline:
Posts: 1,502
Re: What would a voltmeter read if it were connected between the surface of the cylin

Originally Posted by kimm View Post
ra is 6 cm
Oh thanks for clarifing that. It was the ONLY distance in your original question that you did include units for. So what a great idea to repeat that one instead of clarifying the units of the other distances that you didn't include units for. I'm going to give up here.
  Reply With Quote
Old Feb10-10, 07:06 PM                  #8
kimm

kimm is Offline:
Posts: 7
Re: What would a voltmeter read if it were connected between the surface of the cylin

Guys I reallly thought about it but i have not found an answer can some one solve it.
  Reply With Quote
image image
Reply
Thread Tools


Similar Threads for: What would a voltmeter read if it were connected between the surface of the cylinder
Thread Thread Starter Forum Replies Last Post
What does a voltmeter read? JustinLevy Classical Physics 4 Oct30-09 08:05 PM
Two connected particles resting on a smooth cylinder Miss Hannah Introductory Physics 2 Jun30-09 04:30 PM
Circuit with ammeter , what does the voltmeter and battery read sonrie Introductory Physics 5 May5-08 07:49 PM
How do you read this analog voltmeter? FocusedWolf Electrical Engineering 2 Jan28-08 02:32 PM
Where would a voltmeter read 0 in a simple circuit? lollol General Physics 3 Jan3-08 09:08 AM

Powered by vBulletin Copyright ©2000 - 2010, Jelsoft Enterprises Ltd. © 2010 Physics Forums
Sciam | physorgPhysorg.com Science News Partner
image
image   image