A New Perspective of the Force on a Magnetizable Rod inside a Solenoid  

作　　者：José-Luis Jiménez-Ramírez Ignacio Campos-Flores José-Antonio-Eduardo Roa-Neri 

机构地区：[1]Departamento de Física, Facultad de Ciencias, Universidad Nacional Autónoma de México, México D. F., México [2]área de Física Teórica y Materia Condensada, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana Unidad Azcapotzalco, México D. F., México

出　　处：《Journal of Electromagnetic Analysis and Applications》2018年第10期171-183,共13页电磁分析与应用期刊（英文）

摘　　要：We analyze the familiar effect of the pulling of a magnetizable rod by a magnetic field inside a solenoid. We find that the analogy with the pulling of a dielectric slab by a charged capacitor is not as direct as usually thought. Indeed, there are two possibilities to pursue the analogy, according to the correspondence used,?either E → B and D → H, or E?→ H and D?→ B. One of these results in an incorrect sign in the force, while the other gives the correct result. We avoid this ambiguity in the usual energy method applying a momentum balance equation derived from Maxwell’s equations. This method permits the calculation of the force with a volume integration of a force density, or with a surface integration of a stress tensor. An interpretation of our results establishes that the force acts at the interface and has its origin in Maxwell′s magnetic stresses at the medium-vacuum interface. This approach provides new insights and a new perspective of the origin of this force.We analyze the familiar effect of the pulling of a magnetizable rod by a magnetic field inside a solenoid. We find that the analogy with the pulling of a dielectric slab by a charged capacitor is not as direct as usually thought. Indeed, there are two possibilities to pursue the analogy, according to the correspondence used,?either E → B and D → H, or E?→ H and D?→ B. One of these results in an incorrect sign in the force, while the other gives the correct result. We avoid this ambiguity in the usual energy method applying a momentum balance equation derived from Maxwell’s equations. This method permits the calculation of the force with a volume integration of a force density, or with a surface integration of a stress tensor. An interpretation of our results establishes that the force acts at the interface and has its origin in Maxwell′s magnetic stresses at the medium-vacuum interface. This approach provides new insights and a new perspective of the origin of this force.

关 键 词：FORCE on a ROD in a SOLENOID MAGNETOSTATIC FORCE MAXWELL MOMENTUM Balance Equation 

分 类 号：R73[医药卫生—肿瘤]