E-StoreHome » Ask & Discuss » Physics. » Electricity « Back to Discussion
Electricity
17 Mar 2008 21:52:39 IST
0 People liked this
11
693
Is this correct
None
True or False ?
Same amount of maximum charge can be given to a capacitor placed in vacuum and a capacitor placed in air because
q=CV
q=CV
q=
V
now for air and vaccum K=1
q= 
V maximum charge is also same for the two cases
(it is assumed that value of K for vacuum and air are exactly equal and therefore this reason that value of maximum charge is not equal for the two because their values of K are not equal is not valid )
Comments (11)
kundan a.k.a Juan Dankh
Blazing goIITian
Joined: 22 Dec 2007
Posts: 550
17 Mar 2008 22:36:53 IST
Like
0 people liked this
Interesting qs sniper yaar........
i think for the answer to this qs is TRUE......
bcoz the only thing thatcan vary was the dielectric constant.......K
but they have given it to be same.....
rest all
= permittivity of the material (dielectric)and pot diff and resistance aren't likely to change either.....
BUT IT WAS INTRIGUING SO I LOOKED ......
AND U KNOW WHAT......
K DOES VARY FOR VACUUM AND AIR.....
u know free of the dust particles and stuff , the dielectric constant of VACUUM CAPACITORS ARE MORE .......they are in flurry rit now.....
hope it helps
cheers
Reply
17 Mar 2008 23:03:51 IST
Like
1 people liked this
Electric Field between plates cannot exceed 3MV(megavolt)/metre
if it does air becomes conductor (dielectric breakdown) and pot of two plates becomes equal after the spark
hence for vaccum Q max is infinit , not for cap placed in air
(@uperwala as far as k is concerned NOwhere is perfect vaccume)
18 Mar 2008 09:36:59 IST
Like
0 people liked this
i too feel the same way as you have to consider also the dielectric strength too where there is a varience between air and vacuum !!! under the normal conditions we then can say they can but consider the fact that air must not get ionised and we can keep the capacitor in a metal chamber under pressure to prevent this happening !!!!i hope i too am rite!!!
18 Mar 2008 09:42:21 IST
Like
0 people liked this
srini/eistien dielectric breakdown depends on the magnitude of electri field...how will metal chamber help?? do u mean something along the lines of electrostatic shielding??
if so then u r incorrect as the field mis not due to ne external source but it is produced between platec of the capacitor...cud u pls explain ur pt
if so then u r incorrect as the field mis not due to ne external source but it is produced between platec of the capacitor...cud u pls explain ur pt
18 Mar 2008 10:00:26 IST
Like
0 people liked this
Oh cool da gaurav too online ah!!!
nways heres the explaination check even www.wikipedia.org and ncert text books
the whole vandegraff generator is placed inside a metallic chamber under pressure why???
the reason is that as the charge on the outer sphere there is increasing there is a possibilty for the air around to get ionised as air has a certain dielectric strength the metallic chamber prevents charge leakage and pressure prevents ionsiation
here in vacuum you dont have an molecules to get ionsied and thus dielectric strength no defined but air has a certain dielectric strength accepted ah gokul!!!
any contradictions???
18 Mar 2008 10:12:54 IST
Like
0 people liked this
ur explanation is not correct i think
a vandegraff generator is surrounded by a metallic chamber @ high pressure containing nitrogen or methane so as to minimise the leakage of current..only ..i dont see ne explanations regarding the ionisation part...if u c the explanation..it is given tht the van de graff works only upto the field of strength corresponding to dielectric breakdown of air..above which ionization takes place leading to leakage of charge which is minimised by nitrogen/methane @ hihgh pressure
a vandegraff generator is surrounded by a metallic chamber @ high pressure containing nitrogen or methane so as to minimise the leakage of current..only ..i dont see ne explanations regarding the ionisation part...if u c the explanation..it is given tht the van de graff works only upto the field of strength corresponding to dielectric breakdown of air..above which ionization takes place leading to leakage of charge which is minimised by nitrogen/methane @ hihgh pressure
Free Sign Up!
Preparing for IIT-JEE ?
Arihant Revision Package for IIT JEE - Books, Practice Tests + Rank Predictor
@ INR 1,995/-
For Quick Info
Find Posts by Topics
Physics.
Topics
9395
20091
3672
2186
7617
2827
2637
Mathematics.
Chemistry.
Biology
Institutes
Parents
Board
Fun Zone
|
|
|
|
|
| 35,229,755 Engineering Questions Attempted |
6,69,530 Visitors Monthly |
79 Engg. Exam Covered |
392 Students Currently Online |
Connect with Us  |
 |
Vriti Communities
Privacy Policy © Vriti 2011