二、运动电荷的磁场 d db=po sina gv s nguSdl sin a T=nguS uoqvdN sin(v, r) 载流粒子数 dn= nsdi b==, qusin(v,r) dn 4t b= Ro qurI =nqvS dN = n S dl 载流粒子数 二、 运动电荷的磁场 q v × r r B = 3 4π μ o d B = N dB = 4π μ qvsin ( v,r ) r 2 o sin ( ) = qvdN v,r r 2 4π μ o qv r sin = 2 n S dl 4π μ o a 4π μ r d l sin dB = 2 o I a dl q + v S I