NTNUJAVA Virtual Physics LaboratoryEnjoy the fun of physics with simulations! Backup site http://enjoy.phy.ntnu.edu.tw/ntnujava/
January 18, 2021, 03:31:25 pm

Wisdom is to teach our students how to teach themselves. ...Wisdom

 Pages: [1]   Go Down
 Author Topic: How to verify Biot-Savart Law?  (Read 106635 times) 0 Members and 1 Guest are viewing this topic. Click to toggle author information(expand message area).
Fu-Kwun Hwang
Hero Member

Offline

Posts: 3086

 « Embed this message on: January 29, 2004, 09:29:48 pm » posted from:,,Satellite Provider

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
There are 5 translations,
Higher number at the end means more translation been done.
or

The magnetic field set up at point P by the current element i ds
turn out to be
The above equation is called the Biot-Savart law.

The vector dB is perpendicular both to ds (which is the direction of the current)
and to the unit vector r directed from the element to the point P.

The magnetic of dB is inversely proportional to r2 , where r is the distance from the element to the point P.

However, the current must form a loop. You will not have only a small current element.
All the current elements along the current loop can contribute to the magnetic field at point P.
How do we measure magnetic field dB just due to a small current element?
Here is an ideal!

There is no magnetic field in the direction of the current element.
The above two green lines meet at blue dot P.
Current elements from green lines will not produce magnetic field at point P.
The magnetic field at point P is due to current elements from two yellow line sections.
We can keep one of the current element much further away from point P.

Now we have a way to measure the magnetic field just due to one current element.
Click near the right yellow line section and drag the mouse up/down to change its length.
Click near the left yellow line section and drag the mouse up/down or left/right
to change its length and location.

The point P moves when you make the above changes.
The magnetic field at point P is shown at the top left corner.
Click at the DC current source to change its polarity.
You can enter value for the current source into the text Field.
The moving black points represent the electrons moving with average drift velocity.
If you enter a larger value for the current , the electrons will move faster.

Keep increasing the value for the current, until you see the electrons
changing directions -> moving faster -> changing direction ...!

Why is that ? Is there something wrong with the program?
Look at tires of a car when it is accelerating!
Those tires seem to be rotated faster and then change direction ...!

Registed user can get files related to this applet for offline access.
Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list
There are 5 translations,
Higher number at the end means more translation been done.
or
 Logged
Guest
 « Embed this message Reply #1 on: January 30, 2004, 11:11:24 am » posted from:,,Satellite Provider

Subject: Thanks for great BioSavart
Date: Mon, 24 Aug 1998 22:16:57 -0700
From: "Sunpainter" <sunpaint@gte.net>
To: <hwang@phy03.phy.ntnu.edu.tw>
I was looking for something on the shape of circuit for very small circuit
trying to predict some electromagnetic field changes in the circuit.
I will be using very, very small current.
If I had to do all the math for each current change, it would have taken me forever.
Now I have my figures. THANK YOU THANK YOU!
It is for a strange little generator I am building.
Thank you!
K. Hodge Southern California
 Logged
Guest
 « Embed this message Reply #2 on: May 28, 2004, 08:35:12 am »

nipple
 Logged
Worldtraveler
Newbie

Offline

Posts: 1

 « Embed this message Reply #3 on: May 14, 2008, 02:42:27 pm »

Thank You.
 Logged
KentJr
Newbie

Offline

Posts: 1

 « Embed this message Reply #4 on: January 25, 2009, 12:19:54 am » posted from:Baltimore,Maryland,United States

This is fascinating.  Will you please explain why the current changes direction?  It does not seem to make sense to me.
 Logged
Fu-Kwun Hwang
Hero Member

Offline

Posts: 3086

 « Embed this message Reply #5 on: January 25, 2009, 09:26:50 am »

You can click the DC source to change it's polarity.
I think your question is not why it change direction but why flow direction is opposite to the electric field.
Because the moving black points represent the electrons moving with average drift velocity.
It represent electron flow (not the current flow). It was written a few lines below the applet.
 Logged
Joseph123
watchlist
Newbie

Offline

Posts: 4

 « Embed this message Reply #6 on: December 11, 2015, 02:27:59 pm » posted from:Bangalore,Karnataka,India

Good one.Thank You
 Logged
 Pages: [1]   Go Up
Wisdom is to teach our students how to teach themselves. ...Wisdom