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To: Time Traveler who wrote (5853)	4/29/1998 6:59:00 AM
From: Maxwell	Read Replies (2) \| Respond to of 6843

Time Traveller: <<For your super-conductor library, you do not have to achieve zero resistance at absolute zero. Although the DC resistance goes to zero at the super-conducting temperature and material, does the AC resistance also go to zero as well?>> For superconducting material below Tc, the DC resistance is 0. The AC resistance becomes significant above a certain frequency. For Niobium where the Tc=9K the AC resistance becomes significant above a frequency of a few hundred of gigahertz. As a rule of thumb the superconductor becomes a lousy conductor at frequency above its Josephson frequency. For Niobium is 600GHz and for YBCO (ceramic superconductor of Tc=92K) it is about 2000GHz or 2THz. Maxwell

To: Time Traveler who wrote (5853)	4/29/1998 5:30:00 PM
From: Petz	Read Replies (1) \| Respond to of 6843

Time Traveler, re:<your assertion that a+b=a> Your original statement was Junction resistance + trace resistance = junction resistance. found in post 5844. I was merely pointing out that this is true only if b (a.k.a. trace resistance) = 0. This is certainly true at 0 degK, but not for any practical device. Furthermore you seem unfamiliar with engineering jargon, to wit: Although the DC resistance goes to zero at the super-conducting temperature and material, does the AC resistance also go to zero as well? The proper term for "AC resistance" is impedance. I mention Ohm's law only because you should travel back in time to 1827, when it was discovered rather than wasting your time here. Petz