If I build a coil A, of 10cm height with iron core and a 4cm diameter, and alimented it with a DC 15v,6amp source, it will produce a magnetic field. Let’s say A is set vertically. Will building another vertical coil (solenoid) B of the same dimensions and wiring it to a circuit containing LEDs, and placing it at a 5cm of distance to A, light the circuit of LEDs continuously? If no, what can I change to make this idea function?
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\$\begingroup\$ I don't think the term "Alimented" is used in English, it sounds like a poor translation from Portuguese or French. Use "supplied by" or "energized" or simply "coil load". \$\endgroup\$– Vicente CunhaCommented May 25, 2018 at 15:10
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\$\begingroup\$ I'm definitely using Alimented from now on \$\endgroup\$– BeB00Commented May 25, 2018 at 15:17
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\$\begingroup\$ Alimented coil best describes a « coil that is alive » , an alimented coil. \$\endgroup\$– BourhanoCommented May 25, 2018 at 15:21
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\$\begingroup\$ No, in English, "aliment" (as a verb) means "provide with food or nourishment". It does NOT mean provide with energy in a more general sense. If you want to use idiomatic English, say "powered coil". \$\endgroup\$– Dave TweedCommented May 25, 2018 at 16:42
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1\$\begingroup\$ Please don't try to tell a native English speaker what his words mean. That's just rude. Take the constructive criticism in the spirit in which it was intended. \$\endgroup\$– Dave TweedCommented May 25, 2018 at 16:46
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2 Answers
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To induce voltage (and hence be able to drive current) into another coil you need an AC supply on your driven coil. After all you wouldn't expect a DC voltage to be induced in a coil wrapped around a permanent magnet!
To make your set-up function you either have to drive the coil with AC or move the coils relative to each other in the correct way.
Induced voltage = \$N\dfrac{d\Phi}{dt}\$ so flux has to change with time.
answered May 25, 2018 at 15:14
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\$\begingroup\$ N being the number of turns in the second coil? \$\endgroup\$– BourhanoCommented May 25, 2018 at 15:22
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\$\begingroup\$ How about switching on and off the power from the coil A without the need to move anything \$\endgroup\$– BourhanoCommented May 25, 2018 at 15:24
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\$\begingroup\$ Yes, that has the effect of modulating the flux. \$\endgroup\$– Andy akaCommented May 25, 2018 at 15:26
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\$\begingroup\$ And wouldn’t an iron core in B work? What is the need of a permanent magnet? \$\endgroup\$– BourhanoCommented May 25, 2018 at 15:26
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\$\begingroup\$ Read what I said - I was using the example of a permanent magnet with a coil as clearly something that would never work else perpetual motion would be possible! \$\endgroup\$– Andy akaCommented May 25, 2018 at 15:28
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The proposed experiment is what I might expect from someone withOUT engineering training.
Anecdotal response
The air coupling of Electromagnetic energy is called WPT or wireless power transfer. Google sends me a dozen new journal papers on this topic every week. I have sold over 1 million LEDs to a client who has been using WPT for 15 years down under pavement road surfaces and sidewalks for surface emergency sidewalk lighting in tunnels and dynamic lane direction control on roads to support diurnal rush hour direction changes
Lessons learnt.
- Energy loss increases with frequency in both iron core and air gaps.
- but mutual coupling increases with frequency squared and area of the couplers
- path loss is somewhat linear up to coil diameter then 2ord loss after that
- flat ferrite rod and coil can boost mutual coupling
- an accurate plastic cap can boost resonant voltage greatly with no load
- a tapped resonant ferrite rod can match the low impedance of LEDs relative to free space and coil Z(f) boosting current significantly, since weak mutual coupling raises impedance and step-down ratio lowers impedance.
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\$\begingroup\$ If this doesn’t make any sense to anyone try WPT 100k-200kHz or 1 MHz or 21 MHz or license free band. Low frequency. Mutual air coupling is far too inefficient \$\endgroup\$– D.A.S.Commented May 26, 2018 at 6:07
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\$\begingroup\$ Of course, in some parts of the world, 200kHz is slap bang middle of a broadcast band. If you're planning to use it in those places, stay at least 5kHz below 153kHz. \$\endgroup\$– user16324Commented May 26, 2018 at 12:17
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\$\begingroup\$ EU already has 7kW WPT standards for e-charged vehicles at 200kHz and in North America 100kHz with stray shields and C coupled reflectors to block EME Next 14kW is in R&D. So for LEDs this is overkill yet a solid indicator of concept. Others are using wasted AM band from user migration to FM \$\endgroup\$– D.A.S.Commented May 26, 2018 at 14:55