Prof. E. F. Redish 4/4/11 Physics 122 1 4/4/11 1 Physics 122 4/4/11 2 Physics 122 4/4/11 3 Physics 122Prof. E. F. Redish 4/4/11 Physics 122 2 4/4/11 6 Physics 122 4/4/11 7 Physics 122 4/4/11 8 Physics 122 FmgEm→=grav. field of earth =FmgEm→=Prof. E. F. Redish 4/4/11 Physics 122 3 4/4/11 9 Physics 122 E(r) =FqqFq= qE(r)(test charge q placed at the point r)4/4/11 10 Physics 122 g =Facting on mmE =Facting on qqField is the value at a position in space “ r “ assuming that the force is measured by placing the object at r . 4/4/11 12 Physics 122Prof. E. F. Redish 4/4/11 Physics 122 4 4/4/11 13 Physics 122 Field vectors Field lines Careful! Field lines follow the direction of the field. They do NOT follow the magnitude. 4/4/11 14 Physics 122 Field lines for a dipole (colored by strength) 4/4/11 15 Physics 122Prof. E. F. Redish 4/4/11 Physics 122 5 4/4/11 16 Physics 122 Fq=FQ1→ q+FQ2→ q+FQ3→ q+FQ4→ q+ ... Fq=kCqQ1r12r1+kCqQ2r22r2+kCqQ3r32r3+kCqQ4r42r4+ ...where r1= distance from Q1 to q r1= direction from Q1 to q (mag. 1, no units!)r2= distance from Q2 to q r2= direction from Q2 to q (mag. 1, no units!)...4/4/11 17 Physics 122 Fq=kCqQ1r12r1+kCqQ2r22r2+kCqQ3r32r3+ ...Eq=Fqq=kCQ1r12r1+kCQ2r22r2+kCQ3r32r3+ ... Fq=kCqQ1r12r1Eq=Fqq=kCQ1r12r14/4/11 18 Physics
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