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- From: kolstad@cae.wisc.edu (Joel Kolstad)
- Subject: Re: Exam mode in version J (var lock?)
- Organization: U of Wisconsin-Madison College of Engineering
- Date: 23 Jan 93 14:53:59 CST
- Message-ID: <1993Jan23.145359.6066@doug.cae.wisc.edu>
- References: <1993Jan19.164320.14325@doug.cae.wisc.edu> <VgBPXB15w165w@kf8nh.wariat.org> <1993Jan23.192650.21609@netcom.com>
- Lines: 26
-
- In article <1993Jan23.192650.21609@netcom.com> payner@netcom.com (Rich Payne) writes:
- >
- >I have a battery. I measure the voltage with a balanced bridge, so essentially
- >no current flows. How is this possible since voltage is a result? In fact,
- >how are batteries possible?
-
- Well, Rich, I agree with you here. Since voltage is really just
- the potential energy gained or lost by a charged particle moving in an
- electric field. (Although any potential function is only unique to within
- a constant, of course.)
-
- >No voltage, no current.
-
- In general, yes. (One silly exception would be gravitational
- attraction -- place an electron next to a black hole. :-) )
-
- >Said current will never flow without some applied voltage.
-
- In an ideal superconductor, said current will flow. Getting any useful
- work out of said current requires a potential difference. Not to mention
- that real superconductors aren't _quite_ ideal.
-
- Our discussion here should move to e-mail or perhaps
- sci.electronics.what_the_heck_is_going_on_in_this_universe. :-)
-
- ---Joel Kolstad
-