Chapter 25 Magnetism 第十一章稳恒磁场 25-4. Force on an Electric Charge Moving in Magnetic Field ( page586-589) 1. Lorentz force The charged particles moving in magnetic field acted by magnetic force: m mn=9b×B The force Fm acting on a x g/0 charged particle moving with velocity u through a magnetic field B is always perpendicular to v and B
Chapter 25 Magnetism 第十一章 稳恒磁场 25-4. Force on an Electric Charge Moving in Magnetic Field (page 586-589） The charged particles moving in magnetic field acted by magnetic force: 1. Lorentz’s Force x y z o F q B m = v q + v B Fm The force acting on a charged particle moving Fm with velocity through a magnetic field is always perpendicular to and . B v v B
Chapter 25 Magnetism 第十一章稳恒磁场 方向:即以右手四指由经小于180°的角弯向B, 拇指的指向就是正电荷所受洛仑兹力的方向 Fm=q0×B= quBsin a q>0,F=qv×B: q<0,F=-q×B B (when a=0, F=0), Right hand rule Magnetic force only change moving direction WB=0
Chapter 25 Magnetism 第十一章 稳恒磁场 (when = 0,F=0), B v F q Magnetic force only change moving direction WB=0. q F qv B q F qv B = − = 0, 0, ; F q B m = v = qvBsin 方向：即以右手四指 由经小于 的角弯向 ， 拇指的指向就是正电荷所受洛仑兹力的方向. B v 180 Right hand rule
Chapter 25 Magnetism 第十一章稳恒磁场 2. The Motion of Charged Particle in Uniform B (1) Particle moves parallel to B: g: B 0, particle straightly move in constant velocity. (2) Particle moves perpendicular to B: Example 25-4: Electron's path in a uniform magnetic field
Chapter 25 Magnetism 第十一章 稳恒磁场 , particle straightly move in constant velocity. B + q v q - v F = 0 (1) Particle moves parallel to : B 2. The Motion of Charged Particle in Uniform : B (2) Particle moves perpendicular to : B Example 25-4: Electron’s path in a uniform magnetic field
Chapter 25 Magnetism 第十一章稳恒磁场 ⊥B B ××× ×,××、x f=ma ×××××X 1×××a××× 1 ×× u B R ××× We solve for r and find ××、×1×x ××××××0× 0, R qB
Chapter 25 Magnetism 第十一章 稳恒磁场 R q B m 2 0 0 v v = qB m R v0 = B v0 ⊥ F = ma We solve for R and find
Chapter 25 Magnetism 第十一章稳恒磁场 The time t(period of rotation) required for a particle of charge q moving with constant speed to make one circular revolution in a uniform magnetic field is: 2兀R2兀m T vo gB The frequency of rotation is f 1 gB T 2丌m 是回旋加速器( cyclotron)的原理
Chapter 25 Magnetism 第十一章 稳恒磁场 qB R m T 2π 2π 0 = = v m qB T f 2π 1 = = The time T (period of rotation) required for a particle of charge q moving with constant speed to make one circular revolution in a uniform magnetic field is: The frequency of rotation is 是回旋加速器(cyclotron )的原理