計MAGNETIC FLUX 高手幫幫手~.~

a) With reference to the diagram below:

圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Nov10/CrazyEM1.jpg


Due to symmetry, we can first find out the total flux due to 1 wire first and then obtain the final answer by doubling it.

Also, it should be noted that within the range of the wire (i.e. inside the copper), there's no field due to the current flowing in the same wire itself and hence the total flux due to 1 wire can be found as:



圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Nov10/CrazyEM2.jpg


So total flux = 16 ln 2 x 10-6 Wb

b) Similarly, for a single wire, the flux contributed by it inside the region of the other wire is given by:


圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Nov10/CrazyEM3.jpg
Hence the percentage is:

[(2 ln 16/15)/(8 ln 2)] x 100% = 1.12%