• Support PF! Buy your school textbooks, materials and every day products Here!

Determine the points where the net magnetic field is zero

  • Thread starter jisbon
  • Start date
  • #1
391
26

Homework Statement:

A long straight wire lying along x axis carries current I in positive x direction.
Another long straight wire lying along y axis carries current I/3 in positive y direction.
Find points where net magnetic field is zero.

Relevant Equations:

-
Unsure about this, but here is my attempt:

B from the first wire: ##\dfrac {\mu _{0}I}{2\pi r} ##

B from the second wire: ##\dfrac {\mu _{0}I}{2\pi r} ##

Let the point be (x,y)

Can I state that: ##\dfrac {\mu _{0}I}{2\pi y}+\dfrac {\mu _{i}\left( I/3\right) }{2\pi x}=0##

Hence the magnetic field is zero whenever x= -1/3y?

Thanks
 

Answers and Replies

  • #2
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,722
5,031
Homework Statement:: A long straight wire lying along x axis carries current I in positive x direction.
Another long straight wire lying along y axis carries current I/3 in positive y direction.
Find points where net magnetic field is zero.
Relevant Equations:: -

Unsure about this, but here is my attempt:

B from the first wire: ##\dfrac {\mu _{0}I}{2\pi r} ##

B from the second wire: ##\dfrac {\mu _{0}I}{2\pi r} ##

Let the point be (x,y)

Can I state that: ##\dfrac {\mu _{0}I}{2\pi y}+\dfrac {\mu _{i}\left( I/3\right) }{2\pi x}=0##

Hence the magnetic field is zero whenever x= -1/3y?

Thanks
The magnetic field is a vector. You need the vector sum to be zero.
 
  • #3
391
26
The magnetic field is a vector. You need the vector sum to be zero.
So for example in the wire on y axis, can't I assume it will only affect the x direction as the y direction is simply canceled out?
 
  • #4
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,722
5,031
So for example in the wire on y axis, can't I assume it will only affect the x direction as the y direction is simply canceled out?
Certainly the field due to that wire nowhere has a y component. What does that leave?
 
  • #5
391
26
Certainly the field due to that wire nowhere has a y component. What does that leave?
So that leaves a x component, while the wire at the x axis only leaves the y component, hence the equation I put in my thread whereby:
##\dfrac {\mu _{0}I}{2\pi y}+\dfrac {\mu _{i}\left( I/3\right) }{2\pi x}=0##
 
  • #6
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,722
5,031
So that leaves a x component
I do not read the question as restricted to a plane.
Besides, an x component cannot cancel a y component.
 
  • #7
391
26
I do not read the question as restricted to a plane.
Besides, an x component cannot cancel a y component.
So the x component must be equals to 0 too? since the point I am trying to find has no magnetic field
 
  • #8
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
32,722
5,031
So the x component must be equals to 0 too? since the point I am trying to find has no magnetic field
Yes, but but what about my other point? The Newtonian world has three dimensions.
 

Related Threads on Determine the points where the net magnetic field is zero

Replies
7
Views
6K
Replies
2
Views
4K
Replies
3
Views
9K
  • Last Post
Replies
2
Views
1K
Replies
3
Views
2K
Replies
1
Views
1K
Replies
3
Views
3K
  • Last Post
Replies
4
Views
765
Replies
1
Views
1K
Replies
2
Views
247
Top