868_Physics ProblemsTechnical Physics

868_Physics ProblemsTechnical Physics - 208 P30.65 Sources...

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208 Sources of the Magnetic Field P30.65 The central wire creates field B = µ π 01 2 I R counterclockwise. The curved portions of the loop feels no force since A ×= B 0 there. The straight portions both feel I A × B forces to the right, amounting to F B IL I R IIL R == 2 012 2 2 to the right . P30.66 I rB ×× × = 2 2 9 00 10 1 50 10 41 0 675 0 38 7 .. ej e j A Flow of positive current is downward negative charge flows upward or . P30.67 By symmetry of the arrangement, the magnitude of the net magnetic field at point P is BB x = 8 0 where B 0 is the contribution to the field due to current in an edge length equal to L 2 . In order to calculate B 0 , we use the Biot-Savart law and consider the plane of the square to be the yz -plane with point P on the x -axis. The contribution to the magnetic field at point P due to a current element of length dz and located a distance z along the axis is given by Equation 30.3. B r 0 0 2 4 = × z I d r A ± . FIG. P30.67 From the figure we see that rxL z =+ + 22 2 4 and dd z d z Lx z A = + ++ ± sin r θ 2 4 4 . By symmetry all components of the field B at P cancel except the components along
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .

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