Electronics-Lab.com Community

# ren_zokuken01

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1. ## 2 different input AC voltage in a transformer

ok, so we're familiar with a transformer where the AC primary winding induces a magnetic flux in the transformer core which in turn creates a voltage difference and current in the secondary winding. now, i realize this may be a VERY dumb question, but what if we have 2 different AC voltages in the primary and secondary winding. what i mean is that the primary does not induce the secondary voltage and current, but secondary has it's own voltage and current through it. would the core have a sum magnetic flux of the 2 (would work this out in calculus, but as for the physics part, i only know high school level). so would it then create a sum voltage potential?? if we were to put a 3rd winding, would it capture the voltage difference and have current through it??
2. ## Measuring low current on high voltages?

thought so..... T_T what about my idea of a semiconductor device (somewhat like a diode)??
3. ## Measuring low current on high voltages?

how about a semiconductor device that can limit the flow of very high voltage to an upper limit value, but mostly let the current be the same? i guess it also needs to dissipate the heat from said excess voltage very well. does it exist?
4. ## Measuring low current on high voltages?

so i have this electric device that can generate about hundreds of kV of electricity, but low currents. i'd say about tens of milliamperes?? i only need to measure the current. i was thinking of simply using my digital multimeter, so sure, my multimeter can take it coz it's rated to go up until 10A. the thing it's fuse is rated up to only 250V?? so, can i simply remove the fuse from the holder and simply short it? since i already know the current is only gonna be within tens of milliamps? if i do so, can i be sure that the high voltage won't damage my multimeter??
5. ## redirecting 3.5mm jack input

since i still don't have my PC back (thought i am very, very very, very anxiously looking forward to getting it back ASAP), i play my MP3 music from my cheap cellphone. i also happen to have this alarm radio that's got a big speaker. it's got no audio input jack, though. now basically, i want to add a 3.5mm audio input to it. seems easy enough, but my question is, say if i have the radio on, so the pre-amp is taking the audio signals from the radio component. how do i make the pre-amp take the signal from the said 3.5mm jack when i INSTANTLY plug in my phone? i'm getting my jack from here: http://www.digikey.com/product-search/en/connectors-interconnects/barrel-audio-connectors/1443095?k=3.5mm%20jack if i have stereo, do i choose a jack with an internal switch of DPST? coz i remember my high school electronics teacher showing me some sort of jack with a contact leaf that lifts when he plugs in a 3.5mm connector; back when he built an amplifier once.
6. ## gas ignitor for kVs of spark

i want to create electric sparks that can travel through the air of a gap of about 0.5", so i need about 15kV. it only needs to last for about a second or two. i've considered flyback transformers, car ignition systems and neon sign transformers, all 3 are a tad too expensive for the budget. i've looked into stun guns (as i can get one under \$15), but trade of stun guns are prohibited in canada, where i live. so now i've turned to gas/grill/stove ignitors. i've read they can only do a few kV, but i might be able to ramp the voltage a bit more.... the current i have to increase way, way more. maybe a bank of capacitors would do? i dunno... help??
7. ## high voltage electric arc

i need to create voltaic sparks that jumps from one electrode to another between a medium of air. sort of like jacob's ladder. the distance of one electrode to another is about 0.5". i gather that the breakdown voltage of air for said distance is about 4kV. i'm targeting more of around 20-30kV, just to be sure. the sparks do not have to last long, just about 1 sec, max. the purpose of this simple contraption? i want to create a sustained jacob's ladder, rather than one lasting only a second (as the described contraption does). so what this contraption will do is apply the breakdown voltage, ionizing the air and then the sustained high voltage will be supplied by my DC arc welder that outputs 25V @ 50A. don't worry, i won't put the two to be electrically parallel to each other. the contraption has to be very cheap (would simply winding a step-up transformer be enough)?? i've tried different sources, the cheapest i found was simply buying a cheap stun gun (around \$10-20) than can supply a few million volts -- pretty good. but the laws in canada does not allow the trade of any sort of weapon (even for self defense) whatsoever. i've tried looking at neon sign transformers but they cost at least \$50.
8. ## computer speakers

gee, didn't expect great replies in just a short time... i've always assumed that the frequency response was mostly an amplifier issue, not speaker quality... guess that only shows what i know about this stuff, huh? well, i'll do more digging on the subject...
9. ## computer speakers

i've been wanting to buy new high quality computer speakers for some time now, but as cheap as i am, i'm unwilling to go further than \$25. purchasing used ones are a no-no for now. so i was wondering if it is a practical option to actually just swap the amplifier inside my old speaker enclosure with a higher quality one that i could get for a very low price or i could assemble myself??
10. ## 260 Electrical Engineering Books

hi, i'm new here. most obliged if you guys can help find just these 2 ebooks. - The Art of Electronics - TAB Electronic Guide to Understanding Electricity and Electronics tried looking for them in P2Ps, torrent search sites, search engines, till i found this site. i found several links & P2P results for "The Art of Electronics", but most of them is are non-OCR version, w/c aside from ugly, is way too big
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