Maxime Posted January 25, 2019 Share Posted January 25, 2019 hello everyone ! i am a french student in second year of studying and i have some kind of project i chose to study wireless charging system. for my project i have to do experimentations, maths (predict the results) and simulation with a computer. in the maths part i have to calculate the current and voltage output of what would be the device's coil, so i am doing it in two steps: 1/ calculating the magnetic field created by the emmitting coil with definite current and voltage 2/ calculating the current and voltage created by the receeiving coil with the magnetic field upon. however i am having trouble finding formulas etc.. expressing the magnetic field : my physics teacher told me this formula : B=((µ0*I)/(2R))N, with b=magnetic field, µ0= 4pi*10^-7, r the coil radius, N the number of spires. problem is this formula is for such coils (the petrol blue one saying bobine plate) whereas i'm looking for a formula for the coil on the second picture (marroon one with the jzcoil watermarks) i would be grateful if someone could at least tell me the name of the second coil, or point me to a thesis (knowing that the Qi thesis doesn't mention anyting about the magnetic field, except for a simplification just to picture how it would work) merci ! Link to comment Share on other sites More sharing options...
studiot Posted January 25, 2019 Share Posted January 25, 2019 Hello, you need the magnetic field of a flat spiral coil. How is your maths? Here is another experiment to read up on. http://www.scielo.br/pdf/jbsmse/v33n3/a08v33n3.pdf also look here https://www.google.co.uk/search?source=hp&ei=9wdLXLrGAeiqgweBs6XYDg&q=magnetic+field+of+spiral+coil&btnK=Google+Search&oq=magnetic+field+of+spiral+coil&gs_l=psy-ab.3..0l7j0i22i30l3.582.6892..7312...0.0..0.764.6500.1j7j1j4j2j4j1......0....1..gws-wiz.....0..0i131.pb6xLpWwWeA Note this should be in the homework help section. Tell us how you get on. Link to comment Share on other sites More sharing options...
Maxime Posted January 25, 2019 Author Share Posted January 25, 2019 1 minute ago, studiot said: Hello, you need the magnetic field of a flat spiral coil. How is your maths? Here is another experiment to read up on. http://www.scielo.br/pdf/jbsmse/v33n3/a08v33n3.pdf also look here https://www.google.co.uk/search?source=hp&ei=9wdLXLrGAeiqgweBs6XYDg&q=magnetic+field+of+spiral+coil&btnK=Google+Search&oq=magnetic+field+of+spiral+coil&gs_l=psy-ab.3..0l7j0i22i30l3.582.6892..7312...0.0..0.764.6500.1j7j1j4j2j4j1......0....1..gws-wiz.....0..0i131.pb6xLpWwWeA Note this should be in the homework help section. Tell us how you get on. thank you very much for the fast answer! sorry about the wrong section, i will try to move it... thank you for the links ! i will try to update I found this! I have everything I need -for the magnetic field that is- I will come back with results for those interested surely next week Have a nice week end and thanks again :D Link to comment Share on other sites More sharing options...
Phi for All Posted January 25, 2019 Share Posted January 25, 2019 ! Moderator Note Moved to Homework Help. Link to comment Share on other sites More sharing options...
Maxime Posted February 1, 2019 Author Share Posted February 1, 2019 hello everyone ! i am back ;) thanks to studiot i found the answer i was looking for :D i've calculated the magnetic field thanks to the formula in my previous answer. i got for the first coil 0.5mT and for the second 1.5 (or something like that.) so then i moved on ( let me remind you that i want to choose which configuration is better with as the emmiter the bigger or the smaller coil) so i took the formula and isolated the current in order to find it with the magnetic field value found at first. i got to this : for the first setup with the small coil as emmiter and 1A going through it, i got 0.5A out of the recepting end which seems fine by me. but for the second setup, (inversing the two coils) i got 2.5A... so i figured the voltage must drop, (unless i am a genius and found out a way to make infinite energy) and discovered it depends on the number of spires... anyway now i will redo the math with thinner wires for the smaller coil, in order to roughly get the same number of spires and hopefully get decent results. if anyone has ideas, i would be glad to hear about it! maxime Link to comment Share on other sites More sharing options...
studiot Posted February 1, 2019 Share Posted February 1, 2019 Glad it worked out well. A small point to help we call them turns not spires. Spires are pointy roofs, usually on top of towers of cathedrals and university buildings. Link to comment Share on other sites More sharing options...
Sensei Posted February 17, 2019 Share Posted February 17, 2019 On 2/1/2019 at 1:53 PM, studiot said: A small point to help we call them turns not spires. Spires are pointy roofs, usually on top of towers of cathedrals and university buildings. "spires" is French equivalent of "turns".. Link to comment Share on other sites More sharing options...
Maxime Posted February 17, 2019 Author Share Posted February 17, 2019 On 1/25/2019 at 2:56 PM, Phi for All said: ! Thanks for the comment, it just seemed like spire was English and the French wouldn't care to find its own word for it ^^ I just made my own coil, I'll upload a picture once I'm back, in about two weeks Take care Link to comment Share on other sites More sharing options...
Maxime Posted March 15, 2019 Author Share Posted March 15, 2019 Here is the first one ! Diameter is 3-5.7cm Can't upload the Second one as it is too heavy but it's essentially the same with 2-4 cm, both with around the same number of turns Link to comment Share on other sites More sharing options...
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