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Article #114Re: Electric Power in US/Canada: how to compute current?
From: Michael Dix
Date: Wed, 02 Oct 2002 07:49
Date: Wed, 02 Oct 2002 07:49
35 lines
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2731 bytes
Bhoot Nath wrote: > > This is pretty simple question, but at the moment, I can not find a Google > reference. I know that the residential power supply in North America is > 120 volts. > > Q1. Is that 120 volts PEAK of the sine wave, or is that RMS voltage? 120V RMS Most voltmeters assume a perfect sinewave. True RMS meters measure the heating value of the current. > > Q2. If I have a sandwich maker listed as "120V, 60Hz, 900W", how much > maximum current does it draw? Assuming a 100% resistive load, > In other words, will the sandwich maker draw 15 amperes of current? I'm thinking it's 7.5 amps. That's steady state. When you plug it in, the heating element will look like a short circuit at first. The hotter it gets, the more resistive, until it reaches equilibrium. But you might pop a circuit breaker when it first goes on. > Q3. How do I go about computing current drawn by other appliances which > may not be completely resistive? You need to know the power factor. Look at the phase difference between the current and voltage. This reactive current is wasteful because of the IR losses delivering the current to the device, even though the current is not dissipated in the device. -- mjdix@sonic.net
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 11582c,f7f0f2c1f1170335 X-Google-Attributes: gid11582c,public X-Google-Thread: 107518,f7f0f2c1f1170335 X-Google-Attributes: gid107518,public X-Google-Thread: 106595,f7f0f2c1f1170335 X-Google-Attributes: gid106595,public X-Google-Thread: f824f,f7f0f2c1f1170335 X-Google-Attributes: gidf824f,public X-Google-Thread: 105d97,f7f0f2c1f1170335 X-Google-Attributes: gid105d97,public X-Google-ArrivalTime: 2002-10-02 00:50:07 PST Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!nntp-relay.ihug.net!ihug.co.nz!news.ticon.net!feed.news.sonic.net!typhoon.sonic.net!not-for-mail Message-ID: <3D9AA4BB.83D8BCF@sig.please.because.this.is.invalid> From: Michael Dix <look@sig.please.because.this.is.invalid> Reply-To: mjdix@sonic.net X-Mailer: Mozilla 4.77 [en]C-NECCK (Win98; U) X-Accept-Language: en MIME-Version: 1.0 Newsgroups: sbay.general,ba.general,ba.consumers,misc.consumers,sci.electronics Subject: Re: Electric Power in US/Canada: how to compute current? References: <309e7c98.0210011751.51a56500@posting.google.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 35 Date: Wed, 02 Oct 2002 07:49:06 GMT NNTP-Posting-Host: 209.148.113.221 X-Complaints-To: abuse@sonic.net X-Trace: typhoon.sonic.net 1033544946 209.148.113.221 (Wed, 02 Oct 2002 00:49:06 PDT) NNTP-Posting-Date: Wed, 02 Oct 2002 00:49:06 PDT