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

Find loop radius and current via magnetic field?

175
9
1. Homework Statement
A single-turn wire loop produces a magnetic field of 41.2 μT at its center, and 5.15 nT on its axis, at 20.0 cm from the loop center.

Find loop raidus and current.

2. Homework Equations
F = qv x B


3. The Attempt at a Solution
I tried to use the above equation, but could not figure out how to use it to find a radius r. What must be done in order to get an equation with such variables? For current I believe F = IL x B should work, but I don't know if radius r is necessary.
 

Attachments

kuruman

Science Advisor
Homework Helper
Insights Author
Gold Member
8,237
1,812
Sounds like you need to use Biot-Savart to find a general expression for the B-field on the loop axis at distance z from the center, then solve a system of 2 equations and two unknowns.
 
175
9
Sounds like you need to use Biot-Savart to find a general expression for the B-field on the loop axis at distance z from the center, then solve a system of 2 equations and two unknowns.
So I need to use the equation dB = (μ0IdL × Ir)/(4πr2) and solve for r?
 

kuruman

Science Advisor
Homework Helper
Insights Author
Gold Member
8,237
1,812
175
9
Yes, but you need to integrate first. Read and understand the derivation for ##B_z## here.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html
Then use this expression for the two values of ##z## that are given to you. You need to solve for both the current and the radius.
So what z value do I plug in? Also what would be my I? I am confused on how to use this equation. I guess a better question to ask is what does each value correspond to? I am looking at the derivation and am simply confused because this creates a trianlge as far as the diagram shows, but how does this relate to my problem?
 

kuruman

Science Advisor
Homework Helper
Insights Author
Gold Member
8,237
1,812
Forget the derivation and plugging in for the moment. Read the statement of the problem carefully. This loop produces a magnetic field everywhere in space around it. Can you explain to me what you think the given numbers represent? (Fill in the blanks)
Using the coordinate axes in the hyperphysics derivation,
(a) 41.2 μT is the magnetic field at point x = ____, y = ____ , z = ____
(b) 5.15 nT is the magnetic field at point x = ____, y = ____ , z = ____
(c) 20.0 cm is the distance from point x = ____, y = ____ , z = ____ to point x = ____, y = ____ , z = ____.
 

Want to reply to this thread?

"Find loop radius and current via magnetic field?" You must log in or register to reply here.

Related Threads for: Find loop radius and current via magnetic field?

  • Posted
Replies
1
Views
1K
  • Posted
Replies
9
Views
5K
  • Posted
Replies
1
Views
6K
  • Posted
Replies
3
Views
3K
  • Posted
Replies
0
Views
2K
Replies
8
Views
5K
Replies
8
Views
4K
Replies
0
Views
5K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top