平行导线间磁力大小,与电流方向的关系 如下图所示,平行的圆柱导线(形状相同、横截面积一样),通入稳恒直流,且电流强度相等,即 I 1 = I 2 。 情况一 是两导线电流方向相同,出现 吸引 力 f A 。 图 1. 情况一:电流同向。 情况二 是两导线电流方向相反,出现 排斥 力 f P 。 图 2. 情况二:电流反向。 请问,这里的吸引力 f A 、排斥力 f P 的大小是一样的吗? 有没有高精度的物理实验对此进行过检验 ? 1822 年安培的实验结论不用怀疑,但是其精度到底达到怎样的水平? 用途:( 1 )安培定义中需要说明吗?( 2 )大型电力变压器的设计中,需要考虑这些力的作用吗? 俺依稀记得初中制作小直流电动机时,刚通电,线圈中的电线是相互排斥的,稍后就恢复到无电流的状态。应该是没有吸引力 f A 或排斥力 f P 。 假如上面两个图片里,不是导线,而是 两个 电流方向匀 速运动的 点电荷 。则它们之间的作用力大小不等的。假如导线换成 一串 匀速运动的 点电荷 (如 类似糖葫 芦的一串自由 电子),情况会是怎样呢? 感谢您指教! 最好 是物理 实验 的观察 结论 ,而不是逻辑的、理论的分析。谢谢! 相关背景: 1971年Williams、Faller和Hill的实验表明:库仑定律在很大范围极其精确。 这是静止系的实验,没有发现磁场的相互作用。但宇航员、月球人、绝大多数外星人,会有不同的观察现象:磁场是依赖观察者(坐标系、参照系)的。电磁波也是与坐标系有关的。 Williams E R, Faller J E, Hill H A. New experimental test of Coulomb's law: a laboratory upper limit on the photon rest mass . Physics Review Letters, 1971, 26(12): 721-724. http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.26.721 有没有更新的可信实验?
我们都已经熟悉了国内的工业园区和科技园区提供种种优惠政策而吸引投资者、尤其是国外知名公司和高科技企业入驻园区。而这个模式其实连德国著名的科技小城海德堡也同样不能免俗。下面就是新收到的为吸引国际投资者和国际企业入驻海德堡和莱茵-内卡河谷区,海德堡工业园区与海德堡经济发展处联合提供的服务措施。目前包括吸引中国的企业和投资者,也是德国的一个新时尚,因为自去年开始,中国已经成为德国的最大投资国,虽然在金额数量上还远远比不上中国获得的来自德国的投资。 --------------------------------------- Heidelberg Technology Park City of Heidelberg, Economic Development Office Setting up a subsidiary in Heidelberg and the Rhine-Neckar Region Support for international companies Service 1: Test the ground for your company Heidelberg Technology Park offers visits of up to one week to international companies interested in setting up their presence in Heidelberg. This so-called “matchmaking support” provides chances to connect with potential customers, research collaborators or strategic partners. The week-long program for business visitors includes: Office space on the premises of Heidelberg Technology Park with individual address, phone, fax, internet access Postal services: o Letter box with company name o Mail forwarding service Matchmaking support services: o Briefing with Dr. André Domin, General Manager of Heidelberg Technology Park o Tailored research and arrangements of business contacts o Other site information Online publicity Those services are subject to fees. Service 2: Set up a subsidiary in Heidelberg If you have decided to set up a subsidiary in Heidelberg, Heidelberg Technology Park and the City of Heidelberg, Economic Development Office will support your company in this endeavor Services include: Heidelberg Technology Park: Facilities to immediately set up temporary Europe and Germany offices: o Flexible lease o Office space with individual address, phone, fax, internet access o Conference rooms o Administrative support and on-site receptionist o Individual company address o Telephone with voice mail o Mail forwarding service Matchmaking support services o Consulting time with professionals o Monthly programs with experts o Referrals to select service providers o Business subjects workshops o Access to knowledge network o Recruitment of local specialists Economic Development Office Location search: o Individual support in searching for buildings, office space and production sites with suitable business infrastructure in the Heidelberg and Metropolitan area Business support: o Business registration o Application for residence and work permits o Recognition procedures of professional qualifications o Support with applications for funding programs of the German government and European Union as well as other funders o Networking and development of business relationships Family and living support – help with selection and registration: o Support with house-hunting and residence registration o Childcare facilities (nursery, kindergarten) o Schools o Clubs and leisure activities for children and adults o German language and integration courses Information on Heidelberg: its assets and surroundings o Culture o Sports o Events Advantages of a business location in Heidelberg – City of Science and Business in the heart of Germany and Europe Worldwide connections: Frankfurt International Airport is less than one hour away City of Science in the Metropolitan Region Rhine-Neckar (2.4 million inhabitants) Community of knowledge and innovation Symbiosis between science and economy Excellence in research and workforce Proximity to customers and suppliers International community: o International child care facilities and schools, culture, sports, leisure Outstanding quality of life Contact Heidelberg Technology Park Dr. André H.R. Domin, General Manager Im Neuenheimer Feld 582 69120 Heidelberg, Germany Phone: +49 6221 / 5025710 Fax: +49 6221 / 5025711 E-Mail: andre.domin@heidelberg.de Internet: www.technologiepark-heidelberg.de City of Heidelberg Economic Development Office Marktplatz 10 69117 Heidelberg, Germany Phone: +49 6221 / 58-300 00 or +49 6221 / 58-300 01 Fax: +49 6221 / 58-30010 E-Mail: wirtschaftsfoerderung@heidelberg.de Internet: www.heidelberg.de