#### leeyiren

• Jr. Member
• Posts: 39
« on: September 23, 2010, 06:44:09 pm »
Hi prof and the rest,

In the Faraday's solenoid experiment, when you move the magnet quickly into the solenoid, will the needle of galvanometer deflect with a greater magnitude or speed or both? If possible, pls substantiate.

Are there any simulations here to show the change in magnetic flux linkage in the coil? I do not understand how an emf can be set.

Thanks
leeyiren

#### Fu-Kwun Hwang

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• Posts: 3062
« Reply #1 on: September 23, 2010, 06:46:29 pm »

#### leeyiren

• Jr. Member
• Posts: 39
« Reply #2 on: September 23, 2010, 07:13:32 pm »

regarding my first qn, if u insert the magnet at a greater speed, the needle of the galvanometer will deflect at a greater magnitude and speed, right? Any explanations?

From the simulation, I can infer that if you increase the radius of the coil, less current will be produced, right? Any explanations?

By constantly inserting the magnet in and out to produce electricity, will the magnet eventually lose a bit of its magnetism?

Are there any simulations here to show the change in magnetic flux linkage in the coil? not just how the needle deflect.

I would like to see the imaginary magnetic field lines around, esp how the magnetic field lines look when the magnet is inserted into the solenoid?
« Last Edit: September 23, 2010, 07:16:44 pm by leeyiren »

#### Fu-Kwun Hwang

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« Reply #3 on: September 23, 2010, 10:00:12 pm »
Please check out Magnetic field pattern for (line/ coil/ solenoid) for magnetic field line pattern around solenoid.
The magnetic will have the same displacement when you move the magnet (the magnetic field line pattern will not be the same if you can move magnet near speed of light-- which is impossible).

The induced voltage will proportional to the magnetic flux change
\$V=frac{dphi}{dt}=frac{d}{dt}intvec{B}cdot dvec{s}\$

The deflection of galvanometer needle is proportional to the voltage.
Increasing the speed of magnet will increase the rate of flux change.
I will let you think about other questions you have raised.

#### leeyiren

• Jr. Member
• Posts: 39
« Reply #4 on: September 23, 2010, 10:36:00 pm »
but how will the speed of the deflection by the galvanometer be affected? why?

From the simulation, I can infer that if you increase the radius of the coil, the magnetic field will be less distorted inside. but urs have a current flowing in the solenoid. my qn is moving a magnet into a solenoid without any current. Can u explain in words, whether in english or chinese

By constantly inserting the magnet in and out to produce electricity, will the magnet eventually lose a bit of its magnetism? Lenz Law will eventually cause the magnet to demagnetize??

thx

#### Fu-Kwun Hwang

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« Reply #5 on: September 24, 2010, 12:09:49 am »
1. I assume the galvanometer has a very fast response time in the above simulation.
If the response is much larger than the period you move the magnet (in and out),
then the galvanometer will only show small amplitude.
The effect due to finit response time was not consider/implemented in the above simulation.

2. There is always induced current if the solenoid form a close loop (to drive the galvanometer).
Even ther is a current shown in the simulation, it was designed to show the direction of the induced voltage.
The induced current is assume to be very small to cause any significant magnetic flux change.

3. The energy produced is coming from work done by external force.
The magnet will not be demagnetize.

The magnet might be demagnetize very small amount due to your hand warm up it's temperature (normally the effect is much smaller than the experiment error).

#### leeyiren

• Jr. Member
• Posts: 39
« Reply #6 on: September 24, 2010, 12:31:53 am »
what do you mean by the "galvanometer will only show small amplitude
« Last Edit: September 24, 2010, 12:36:06 am by leeyiren »

#### Fu-Kwun Hwang

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• Posts: 3062
« Reply #7 on: September 24, 2010, 05:43:51 am »
The galvanometer is driven by current flow which will generate torque to drive the rotational motion of the needle.
The ineritial of the needle will determined the response time.
If the ineritial is too large, the needle will move slowly.
if the movement of the manget change direction before needle reach it's maximum amplitude,
the current flow in opposition direction, then the torque will change direction.
So the amplitude will become smaller than it's possible maximum value.

You are welcomed to check out my Physics discuss forum(in Chinese) if you can understand Chinese.

#### leeyiren

• Jr. Member
• Posts: 39
« Reply #8 on: September 25, 2010, 11:46:28 am »
i would like to.....but i dun read   . why dun use ? less complicated.

#### Fu-Kwun Hwang

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• Posts: 3062
« Reply #9 on: September 25, 2010, 10:00:27 pm »
There is a button which will turn all the traditional chinese characters into simplify chinese (GB2312 code).

For you, the simplify chinese is less complicated because you are more familiar with it.
For me, traditional character is more meanful.

I just provide you another option. It is your choice to use it or not.

#### lookang

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• Posts: 1774
• http://weelookang.blogspot.com
« Reply #10 on: September 25, 2010, 10:52:42 pm »
i am using Chrome Browser and it translate into english in http://www.phy.ntnu.edu.tw/demolab/phpBB/viewforum.php?forum=130

i see a lot of cool stuff not in the http://www.phy.ntnu.edu.tw/ntnujava/index.php

example of the translation:
Department of Physics, National Taiwan Normal University physics teaching classroom demonstration experiment(oldsite) physics forum (Huangfu Kun)
We have also commenced for the establishment of science teaching and learning systems:the Science Parkto get the teacher more convenient use of network technology in teaching, Teachers are welcome to make use of it! Physics (Wikipedia)
(Not just know HOW to study physics is more important is know WHY, welcome to the world famous reference tothe physical animation, English websiteNTNUJAVAto animation-based) news coverage

Keywords  RecentlyDay to retrieve the physical terms in the British system can not log in, or return of function is not normal
Electromagnetic and Electronic Circuits related videosManagers::Huangfu Kun |
Forum Home >>instructional videos >>Electromagnetic and Electronic Circuit Videos (order by reading a few)
[Lookang] to our time 1778 seconds, reading 22 pages, 21 points reward, the recent record here in Singapore Singapore location features on the forums / suggestions for improvement of physical concept test area
Are you interested in testing their own physical strength? Newphysics concept test zone has more than two hundred multiple choice.

Huang Fukun modify, transfer into Chinese layout and increased functionality
Any questions on this forum pleaseLetter to provide improvements!

#### ahmedelshfie

• Hero Member
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« Reply #11 on: September 26, 2010, 02:01:05 am »
I want to say Google Chrome Browser is a new browser developed by Google and
Any user available to translation to any language in the same page
« Last Edit: September 26, 2010, 02:05:01 am by ahmedelshfie »

#### leeyiren

• Jr. Member
• Posts: 39
« Reply #12 on: September 26, 2010, 11:20:52 pm »
cool.

i just tried both of ur suggestions. Indeed google chrome can easily change fanti to jianti and chinese to english at lightning speed.

I will be looking forward to utilise ur forum in future.

#### Fu-Kwun Hwang

• Hero Member
• Posts: 3062
##### Chinese version of physics forum or resources
« Reply #13 on: September 27, 2010, 10:16:08 am »
I do not have time to translate all Chinese physics learning/teaching resources into English.
This forum only contain simulations I have developed.
You are welcomed to check out http://www.phy.ntnu.edu.tw/demolab/ or http://www.phy.ntnu.edu.tw/Demolab/ for more Chinese version physics resources. You will find physics demonstration, everyday physics, physics toys, physics activities,...

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