The figure shows an end view of two long, parallel wires perpendicular to the xy plane, one at (0, a) and one at (0, -a), each carrying currrent I = 25.0 A, but out of the page at (0, a) and into the page at (0, -a). a) Find an expression for the magnetic field on the x axis, magnitude and direction, in terms of x and given quantities, using a=5.00 cm. b) At what value of x is the magnitude of! B the greatest? c) What is an approximate expression forB when x >> a? 兩電流一個往+Z方向,一個往-Z方向 (a)我算的問題請問積分是由z=負無限到正無限嗎? 因為它的改變在x但對z做積分感覺完全沒有影響呀 那後兩題不就跟x沒關係這它這樣問好像怪怪得Q_Q 能否有大大可以給我指點一下 謝謝^^ --

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