Yesterday's Tractor Co. Shop Now
   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver
Classified Ads
Photo Ads
Tractor Parts

Discussion Forums
Project Journals
Tractor Town
Your Stories
Show & Pull Guide
Events Calendar
Hauling Schedule

Tractor Photos
Implement Photos
Vintage Photos
Help Identify
Parts & Pieces
Stuck & Troubled
Vintage Ads
Community Album
Photo Ad Archives

Research & Info
Tractor Registry
Tip of the Day
Safety Cartoons
Tractor Values
Serial Numbers
Tune-Up Guide
Paint Codes
List Prices
Production Nbrs
Tune-Up Specs
Torque Values
3-Point Specs

Tractor Games
Just For Kids
Virtual Show
Museum Guide
Memorial Page
Feedback Form

Yesterday's Tractors Facebook Page

Related Sites
Tractor Shed
Ford 8N/9N Club
Today's Tractors
Garden Tractors
Classic Trucks
Kountry Life
Tractor Talk Discussion Forum

Re: Solid vs stranded wire

[Show Entire Topic]  

Welcome Guest, Log in or Register
Author  [Modern View]

10-15-2013 18:22:32

Report to Moderator

Stranded is for vehicle use because it is flexible enough to avoid fatigue breakage when moved and vibrated. Not the case in house wiring. There is an effect, but at high frequencies, not enough to even consider at 60 Hz in AC house wires. Jim

The following is from Argon National Laboratory:

DC current will use the wire's whole cross-section evenly.

Imagine a single solid wire divided by invisibly-thin barriers into parallel strands of equal thickness and shape. Only at the ends are they joined together, metal-to-metal. In this picture, each strand has equal resistance, and equal voltage from end-to-end, so the current in each is equal.

Only AC has a preference for a particular depth. It prefers to be shallow, staying towards the outside. This is a consequence of changing magnetic fields caused by the changing current.

If it is DC, it is not changing, so the magnetic field is steady, and has no effect on the DC current density. DC current only cares about resistance, not inductance or magnetism.

Weird but moot minor point: The steady field around a wire with DC current may cause a small voltage difference between the outside and the inside. However the difference at one end cancels out the difference at the other.

Due to electromagnetism, parallel currents attract. So if the metal conducts electrons, then they are squeezed inwards, and the interior would be slightly more negative than the outside. Contact at the starting end is made to the wire's outside. So is contact at the finishing end. So an electron going travelling the wire-center route may go up a small potential step at the start, then go down the same amount at the end. These two steps cancel each other out. The end-to-end voltage in the wire interior is the same as the wire exterior, so the current densities are the same too.

Nobody even thinks about those last two paragraphs. They do not need to. Except maybe physicists doing plasma hi-power sparks with Z-pinch. Z-pinch is when the glow of the current in the ionized gas spontaneously squeezes itself into a very intense sharp narrow strand, even though it started out wide and diffuse. It only does that if the current is very high, and because a gas can be compressed. In a solid metal the mobile electrons (charge -1) are forced to keep a constant density by the need to keep charge neutrality with the hard-packed metal-ions (charge +1) they wander amidst.

Jim Swenson

[Log in to Reply]   [No Email]
[Show Entire Topic]     [Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:

Fast Shipping!  Most of our stocked parts ship within 24 hours (M-Th). Expedited shipping available, just call! Most prices for parts and manuals are below our competitors. Compare our super low shipping rates! We have the parts you need to repair your tractor. We are a company you can trust and have generous return policies. Shop Online Today or call our friendly sales staff toll free (800) 853-2651. [ About Us ]

Home  |  Forums

Copyright © 1997-2018 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters