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

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## Force on a current carrying conductor inside the magnetic field

We know that a current carrying conductor has a magnetic field arround it.

Now if it is placed in a uniform magnetic field of some other magnet, then there will be two magnetic fields, one due to cuurent in the conductor and the other due to magnet. The interaction of these two magnetic fields will result in a net force that will act on conductor. It can be explained as follow.

Let us consider that a uniform magnetic field exists in certain region in upward direction. A current carrying conductor is placed in it at right angles to the direction of magnetic field such that the current in the wire is directed out of plane. It can be shown with a sign of dot.

The magnetic lines of force due to current in the conductor will be in the plane of paper and can be shown by concentric  dotted circles.

From the above figure it can be seen that on the right hand side of conductor the magnetic field due to current in the conductor is in the same direction as that of field in which it is placed so they will support one another. Hence the magnetic field on right side will be strong.

On the left hand of conductor, the two magnetic fields (because of current carrying conductor and magnet) are in the opposite direction so they cancel the effect of each other. So on the left side the magnetic field will be weak.

Thus on one side of the conductor, net magnetic field strong and where as on the other side net magnetic field is weak. As a result a force on conductor towards left side where the field is weak.

The above fact can be demonstrated by a simple experiment.

A brass rod is placed on two parallel brass rails which are connected across a battery. The two rails lie in the resgion between pole pieces of U- shaped magnet.

The brass rod R, the two rails and battery make a closed circuit. When current passes through the rod, it rolls along the rails.

Fleming’s left-hand rule:

Whenever a current carrying conductor is kept inside the magnetic field, it experiences force. The direction of force on conductor relative to direction of current and applied magnetic field can be described by Fleming’s left-hand rule which is as follows.

If forefinger, middle finger and thumb are stretched perpendicular to each other such that forefinger points in the direction of applied magnetic field and middle finger points in the direction of electric current then thumb will point in the direction of force on a conductor.

The magnitude of force on a current carrying conductor in a uniform magnetic field is directly proportional to the amount of current inside the conductor, length of the conductor inside the magnetic field and strength of magnetic field. It also depends on the angle between direction of current and that of magnetic field.

If conductor is placed at right angles to the direction of magnetic fields, then magnitude of force will be maximum and if it is placed along the direction of field, then this force will be zero.

 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.------------------------------------------------------------------------------------- Admin Replied:  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

 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