From: Farley Flud Subject: Re: To All The Pseudo Engineers 2 Newsgroups: comp.os.linux.advocacy References: User-Agent: Pan/0.146 (Hic habitat felicitas; d7a48b4 gitlab.gnome.org/GNOME/pan.git) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Lines: 50 Path: ...!news.misty.com!weretis.net!feeder9.news.weretis.net!usenet.blueworldhosting.com!diablo1.usenet.blueworldhosting.com!feeder.usenetexpress.com!tr2.iad1.usenetexpress.com!news.usenetexpress.com!not-for-mail Date: Thu, 16 Jan 2025 13:47:46 +0000 Nntp-Posting-Date: Thu, 16 Jan 2025 13:47:46 +0000 X-Received-Bytes: 1934 Organization: UsenetExpress - www.usenetexpress.com X-Complaints-To: abuse@usenetexpress.com Message-Id: <181b305f30d41aa1$3764$2484$802601b3@news.usenetexpress.com> Bytes: 2342 On Wed, 15 Jan 2025 10:55:43 +0000, Farley Flud wrote: > > Often, when an electronic device is plugged into the power > outlet there will be sparking. > > Explain, using explicit mathematical equations, why this > happens. > Ha! All of the fat mouths have failed. This is freshman stuff. Very basic. I shall explain. Every circuit has inductance, even if the inductance is totally parasitic. The equation for the voltage across an inductor is the following: delta V = -L * dI/dt So the voltage is proportional not to the current (I) but to the rate of change of current (dI/dt). Thus, when a circuit is "plugged in" or connected to the mains power source, the current begins to flow from zero. The rate of change (dI/dt) is extremely large and so is the voltage. The voltage is so large that it causes a dielectric breakdown of the air, i.e. a spark (a mini lightning bolt). Actually, due to the electric field of the mains, the current actually begins to flow before contact is made. The spark will jump across the small gap. At times, the spark is so hot that it can cause pitting of the metal contacts. This phenomemon will happen all the time. There is no way to avoid it, other than perhaps to make contact at zero volts and then turn the voltage up after contact is made. Oblinux: I say so. -- Hail Linux! Hail FOSS! Hail Stallman!