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Rev. Notes > IGCSE > Electromagnetic Effects
 
 
Previous Topic Electromagnetic Effects Next Topic

Topics
 

Induced e.m.f.

Factors affecting the magnitude of induced e.m.f.

Lenz's law

A.C. Generator

Rotating-coil generator and use of slip rings

Graph - output voltage against time for an A.C. Generator

Transformer

Advantages of high voltage transmission

Energy losses in transformer

Magnetic field due to a current in a straight wire

Magnetic field arroud a current carrying solenoid

Force on a current carrying conductor inside the magnetic field

D.C Motor

Difference between slip rings and split rings

Test Yourself

 

-

A.C. Generator

The diagram below shows a simple A.C. generator , which provides the current to a small bulb. The coil is made up of insulated copper wire and is rotated by turning the shaft. The slip rings are fixed to the coil and rotate with it. The brushes are two contacts  which rub against the slip rings and keep the coil connected  to the outside part of the circuit. They are usually made up of carbon, that is why they are called carbon brushes.

A.C. Generator

When the coil is rotated, it cuts magnetic field lines, so an e.m.f. is generated and electric current flows. As the coil rotates, each side move continuously upward and downward, in side the magnetic field. So the c electric current flows backward and forward i.e. A.C. (Alternating Current). Below graph shows the output of the A.C. generator.

The graph shows, how the current varies when the coil rotates. It is a maximum when the coil is cutting the magnetic lines of forces at the maximum rate. It is zero when the coil is vertical and no magnetic lines of forces are cut by it.

The magnitude of induced electric current increases by increasing the following factors.

  • Increasing the number of turns in the coil
  • Increasing the area of the coil
  • Using a stronger magnet
  • Rotating the coil faster
 
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View Comments on this Chapter - Total Comments (40)
 
Munawar Ahmed Said :
Dear Sir, A brilliant try for motivating IGCSE student but please try to convey in colourful manner
 
  14/10/16 09:17 PM
   
Allan Said :
The answer looks a little lite on information. I take it there's proably room for more info on the slip ring difference, and how this impacts the electromagnetic field, no? Any thoughts of expanding it? Resources like this might be a good source of info: http://powerbyproxi.com/slip-ring/ . That, or a quick google search ;/ Just a thought! Otherwise, the comments section has been super helpful. Thanks
 
  30/09/16 03:23 AM
   
DIVYANSHU SAINI Said :
AND WHAT ABOUT THE POWER LOSES
 
  02/05/16 09:13 AM
   
DIVYANSHU SAINI Said :
WHICH WILL INDUCE MORE E.M.F (A) IF A CYLINDRICAL MAGNET IS ROTATED INSIDE A COIL (B) IF COIL IS ROTATED IN AN MAGNETIC FIELD OF SAME STRENGTH (C) IF THE CYLINDRICAL MAGNET IN (A) IS REPLACED BY SOME OTHER TYPE OF MAGNET (ie. BY A BAR MAGNET OR A MAGNET IN FORM OF A CYLINDER BUT HAVING GAPS AS IN AN ELECTRIC MOTOR) PLEASE NOTIFY ME ON DIVYANSHUMRWAL@GMAIL.COM IF YOU CAN. AND PLEASE REPLY WITH REASONS THAT WHY WHY THIS OPTION AND WHY NOT. AND ONE THING MORE "INSTENTLY"
 
  02/05/16 09:05 AM
   
Mohammed Ilyas Said :
Haris you should mention that the thumb has to be in the direction of the current in the wire
 
  06/10/15 08:34 PM
   
z Said :
not much information needs improvement
 
  06/10/15 08:22 PM
   
Mohammed Ilyas Said :
Isn't the equation Vp x Ip = Vs x Is? that's how i found it in some other sources
 
  06/10/15 08:16 PM
   
haris Haseeb Said :
How to apply right hand grip rule ? Hold a wire in your hand. The thumb shows the way of current flow and the fingers shows us the magnetic field is it right sir ...?
 
  06/10/15 07:59 PM
   
hudeyfa ali Said :
thanks
 
  06/10/15 07:28 PM
   
abdulrahman murad Said :
An electric current passes through a solenoid, resulting in a magnetic field. When wrapping the right hand around the solenoid with the fingers in the direction of the conventional current, the thumb points in the direction of the magnetic north pole.
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Admin Replied:

yes Great!

 
  06/10/15 06:57 PM
   
hudeyfa ali Said :

what is right hand grip rule and how to apply it ?

 
  06/10/15 06:39 PM
   
unknown Said :

what is kick?

 
  03/10/15 08:19 PM
   
feras maen Said :
what do you assume,when you apply the transformer equation VpIp=VsIs Ans. We assume that the transformer is 100% efficient.
 
  03/10/15 04:52 PM
   
hudeyfa ali Said :

thanks

 
  03/10/15 01:38 PM
   
hudeyfa ali Said :

can you please answer Q.19 ?
-------------------------------------------------------------------------------------
Admin Replied:

Thanks for your remarks

Visit this link http://www.physicsatweb.com/rev.php?id=Electromagnetic%20Effects&rid=7

 
  03/10/15 11:44 AM
   
Mohammed Adel Said :

I haven't understood it yet
-------------------------------------------------------------------------------------
Admin Replied:

Thank you very much for your remarks. In which topic you are facing difficulty to understand? Can you please mention that? We are always here to assist you.

 
  28/09/15 04:57 PM
   
Saiba Muhammed Said :

I can not see the picture could you please upload it soon...?
-------------------------------------------------------------------------------------
Admin Replied:

If you are asking for an article of "induced e.m.f.", then it is already uploaded. Thanks

 
  19/05/15 04:08 PM
   
Anon Said :
Its Vp/Vs=Is/Ip
 
  27/04/15 03:28 PM
   
Anonymous Said :
Its meant to be Vp/Vs=Ip/Is Not Vp/Vs=Ip=Is
 
  22/03/15 09:27 PM
   
Anonymous Said :
Its meant to be Vp/Vs=Ip/Is Not Vp/Vs=Ip=Is
 
  22/03/15 09:27 PM
   
okolie victor (imsu) Said :
ok but pls more details
 
  17/10/14 06:10 PM
   
victor okolie Said :
please can I see the diagram
 
  17/10/14 06:06 PM
   
tammy gibson Said :
i think you should add the effects of on the output voltage if the coil is made to turn faster
 
  11/08/14 05:34 PM
   
Anonymous Said :
The site is very good but please check your grammar i.e you made many typing errors.
 
  06/07/14 11:52 AM
   
Professor joe Said :
I think that some more effort is to be put in it. Thereafter I want to say that igcse is easy. Just log on to some appropriate sites and videos. Kapish. Yo
 
  13/04/14 04:37 PM
   
lppen Said :
they were no notes
 
  26/03/14 08:16 PM
   
Nisar Said :
Everyone says that P=I^2.R, And by having high voltage we have low current, so low energy losses but another formula, P=V^2/R, According to this if voltage will be increased Power Loss will also be increased.....How we will justify this????????/
 
  06/03/14 05:46 PM
   
dinesh Said :
thanks
 
  15/02/14 07:45 PM
   
Kunal Mshra Said :
This Diagram Really Explains alot.
 
  10/12/13 07:42 PM
   
electricslipringcom Said :
JINPAT Electronics is a leading manufacturer in industrial slip rings. We commit ourselves to the development, designing and manufacturing of different types of high quality slip rings for a vast variety of applications. We provide standard products as well as customized products according to your needs. We have also collaborated with Consortium of Industry including Military Industry and Universities in China. http://www.electricslipring.com/
 
  26/09/13 11:12 AM
   
dalha nigeria Said :
why not list the factors above and later explain them for easy identification
 
  20/08/13 12:54 AM
   
alvin xavier Said :
derivations shud b provided
 
  04/03/13 05:24 PM
   
claire Said :
Where are the diagrams?????
 
  13/01/13 09:29 AM
   
Adan Said :
Very useful but will be great if diagrams were added to explain more.
 
  21/11/12 12:11 PM
   
Nabila Said :
The notes are very helpful but there are no pictures or diagrams to make the student understand more. These might be small things but there are very helpful for a student.
 
  20/09/12 08:49 PM
   
kishor Said :
its usefull
 
  29/07/12 04:28 PM
   
sarah Said :
you spelled generator wrong its not gennerator :)
------------------------------------------------------------------------------------- Admin Replied:

Thanks for pointing that out sarah, we will edit the notes soon so that they are more accurate. Keep visiting

 
  30/04/12 06:01 PM
   
Gia Said :
can u please add some pictures on AC generators and DC motors? thank you!
------------------------------------------------------------------------------------- Admin Replied:

Thank you, We will try our best to post more illustrations of AC generators & DC motors. Just stay tuned.

 
  27/04/12 07:01 PM
   
harshil Said :
its to short and not explained properly with image
------------------------------------------------------------------------------------- Admin Replied:

Thank you for your comment, we will make sure we provide further explaination asap.

 
  03/04/12 03:05 PM
   
kazakh Said :
there is no image
 
  18/02/12 06:09 PM
 

 

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