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Capacitors
Posted by biswarup on 3/5/2004, 11:22 pm I know this sounds stupid, but could you please tell me about the different units of capacitance? My tank cap should ideally be 0.053 uF. How do you say uF & nF (like 'kilometer' for km), and what in the unit of microfarads? I need to know this coz in India, everyone sells caps by MFDs (microfarads). The dealers can't even tell me about the different units!!
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Re: Capacitors
Posted by Bert Hickman on 3/5/2004, 11:47 pm, in reply to "Capacitors" Hello, A microfarad is shortened to uF and is equal to 10^-6 farad. A nanofarad (nF) is equal to 10^-9 farad. A uF is 1,000 times larger than a nF, so converting from uF to nF means moving the decimal point three places to the right. So, 0.053 uF is the same as 53 nF, and 0.0053 uF is the same as 5.3 nF. A nF is 1,000 times larger than a picofarad (pF). A pF is 10^-12 farad. Hope this helped! Best regards, -- Bert --
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Capacitors (Again!)
Posted by biswarup on 3/5/2004, 11:37 pm, in reply to "Capacitors" How good is a saltwater cap? I plan to build them for my 4" TC powered by a 15kV NST @ 30mA. What is the appox capacitance of and individual 1l/2l plastic coke bottle filled with about 3/5 saltwater? Should I use saltwater or will other sols. be better like dil HCl (from bathroom acid called 'muriatic acid')? Should I use glass bottles?
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Re: Capacitors (Again!)
Posted by Bert Hickman on 3/6/2004, 12:07 am, in reply to "Capacitors (Again!)" Hello again, Don't use plastic bottles for your caps - they will either immediately break down or they'll heat up and rapidly break down under the high voltage RF stress. Salt water is very much preferred to using muriatic (hydrochloric) or any other acid for that matter. Salt water is simply much safer and inexpensive. Acids offer absolutely no performance benefit, and bottles often break when used in Tesla tank circuits - it's not good to suddenly have acid all over your floor or table (or you!). Also, make sure you use use glass bottles. A glass beer bottle (650-700 ml) will provide about ~650 - 800 pF/bottle, so you need somewhere around seven or eight beer bottles to get up to ~5300 pF (5.3 nF). However, you may also need to connect pairs of beer bottles in series so that the pairs can withstand the voltage stress from your 15 kV NST. If you begin to puncture single bottles, using pairs of bottles should stop this. However, you'll need to use four times the bottles to get the same capacitance, since connecting the bottles in series will result in getting only half the capacitance (350 pF) per pair of bottles. Good luck and play safely! -- Bert --
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