Home » Ask & Discuss » Physics. » Electricity « Back to Discussion

Electricity

New kid on the Block

Joined:	24 Jun 2007
Post:	6

1 Jul 2007 19:46:55 IST

0 People liked this

376

have guts to do it?????????

None

an infinite no. of charges each =Q r placed along X axis at x=1,x=3,x=9..............(in m)find potential and electric field strength at x=0,if

-consecutive charges have opposite sign

-consecutive charges have same sign

Share this article on:

Comments (4)

Souvik gupta

Hot goIITian

Joined: 30 Jun 2007

Posts: 107

1 Jul 2007 21:49:01 IST

Like 1 people liked this

If the consecutive charges are of same sighn then net electric field is KQ*9/8. and potential isKQ*3/2.
In the other case electric field iskq*72/80
if you need the soln then ask for it you will get that too

Neeraj Agarwal

Blazing goIITian

Joined: 22 Jan 2007

Posts: 2039

2 Jul 2007 12:31:27 IST

Like 0 people liked this

When they have opposite signs....
potential = kQ(1 - 1/2 + 1/3+-............) = kQln2

edison

Forum Expert

Joined: 19 Oct 2006

Posts: 7537

2 Jul 2007 13:48:38 IST

Like 0 people liked this

Q) an infinite no. of charges each =Q r placed along X axis at x=1,x=3,x=9..............(in m)find potential and electric field strength at x=0,if

-consecutive charges have opposite sign

-consecutive charges have same sign

Sol) Potential at x = 0 due to consecutive charges of same sign

V_like = kQ/r1 + kQ/r2 + ...

or V_like = kQ (1 + 1/3 + 1/9 + ...)

here the term in the bracket is GP with common ratio of 1/3, so

(1 + 1/3 + 1/9 + ...) = 1/ (1-1/3) = 3/2

thus V = 3kQ/2, for like charges.

But for comsecutive opposite charges the expression is

V_opposite = kQ (1 - 1/3 + 1/9 - ...) = kQ / ( 1+ 1/3) = 3kQ/4

V_opposite = 3kQ/4

Similarly for electric field due to like charges the expression is

E_like = kQ (1/1² + 1/3² + 1/9² + ...)

or E_like = kQ (1/1² + 1/3² + 1/3⁴ + ...)

here common ratio = 1/3²

so E_like = kQ / (1-1/3²) = 9kQ/8

but for opposite charges the case is

E_opposite = kQ (1/1² - 1/3² + 1/3⁴ - ...) = kQ / (1+ 1/3²) = 9kQ/10

Neeraj Agarwal

Blazing goIITian

Joined: 22 Jan 2007

Posts: 2039

2 Jul 2007 17:32:13 IST

Like 0 people liked this

sorry for the wrong solution of mine....
i didn't read the question properly....

Quick Reply

Reply

	Some HTML allowed.
	Keep your comments above the belt or risk having them deleted.
	Signup for a avatar to have your pictures show up by your comment
	If Members see a thread that violates the Posting Rules, bring it to the attention of the Moderator Team