磁场magnetic-1课件.ppt

Chapter 4 ;Magnetic fields in this chapter: 本章研究的磁场; * 2. the actions of M field to electric current 磁场对电流的作用; * 3. electric currents produce magnetic fields. 电流产生磁场;§4.1 The M force M field;I;M lines of current-carrying solenoid 通电螺线管的M线;Character of M lines: M线的特征;2) M lines do not cross. 磁力线不相交。 ;2. Magnetic force (物理学，P128，148-172); What conditions the particle to test E field must satisfy? 测试电场的电荷必须满足什么条件？;If we put one moving test charged particle with in a M field ，the magnetic force :;Three vectors, perpendicular to each other;Note: if the test charge is negatively charged, the direction of the M force is opposite.;E force and M force on charged particles 点电荷的电力和磁力; Because the M force is always perpendicular to the M field. 磁场力总是与磁场方向垂直。;Motion of a charged particle in a constant M field;The angular speed of the particle is;x;Applications of the motion of a charged particle in M field带电离子在磁场中运动的应用;1) Velocity selector 速度选择器;2) The mass spectrometer 质谱仪;3) Cyclotron 回旋加速器;After many cycles, the particle arrives the boundary of the container. At this time, the cyclotron radius is the radius of the container R0.;3. Magnetic field ;The M field obeys the superposition principle, like E field.;§4.2 M force on a current-carrying conductor 载流导体上的磁场力;One charged particle;× × × × × × × × ×;I;More generally, an arbitrarily shaped wire of uniform cross section in an external M field: 横切面积均匀的任意形状的 导线在磁场中的受力;Arbitrary shaped wire;3) Current loop in M field 磁场中的环形电流;The net M forces on the rectangular loop carrying a current is zero.;I;If the M field makes an angle of θto the plane，the net torque;Magnetic dipole moment/magnetic moment 磁矩;If the coil consists of N turns of wire, each carrying the same current and each having the same area, the total magnetic moment of the coil is:如果一线圈由N匝导线圈组成，并且每匝导线圈有同样的电流和同样的面积，线圈的磁矩是：;Example 4-1;§4.3 The Biot-Savart Law 毕奥－萨伐尔定