※ 引述《ian60702 (pacific hero)》之铭言： : A length of copper wire carries a current of i A uniformly distributed through : its cross section,what is the energy density of the magnetic field at the : surface of the wire?(the wire diameter is 2R) : u(i^2) : 答案给───── : 8(R^2) : 请问是不是少除了pi平方? : 还是在下观念有误....烦请高手指点...感恩 B*2πR=μI μI B=------- 2πR B^2 μI^2 u=------ = -------- 2μ 8πR^2 好像没错 --

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