184_notes:magnetic_field

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184_notes:magnetic_field [2018/05/15 17:39] – curdemma184_notes:magnetic_field [2021/07/06 17:30] – bartonmo
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 Chapters 17 and 20 of Matter and Interactions (4th edition) Chapters 17 and 20 of Matter and Interactions (4th edition)
  
-[[184_notes:conservation_theorems|Next Page: Conservation Theorems]] +/*[[184_notes:conservation_theorems|Next Page: Conservation Theorems]] 
  
-[[184_notes:electric_field|Previous Page: The Electric Field]]+[[184_notes:electric_field|Previous Page: The Electric Field]]*/
  
 ===== The Magnetic Field ===== ===== The Magnetic Field =====
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 {{youtube>gOrcYltPW3E?large}}  {{youtube>gOrcYltPW3E?large}} 
-==== Model of a moving point charge ==== +===== Model of a moving point charge ===== 
-{{  184_notes:bfieldpoint.png?200}}+[{{  184_notes:bfieldpoint.png?200|Magnetic field from a moving point charge}}]
  
 Our introduction to the magnetic field started with [[184_notes:moving_q|a single moving charge]]. We observe the magnetic field produced by a single moving charge to be, Our introduction to the magnetic field started with [[184_notes:moving_q|a single moving charge]]. We observe the magnetic field produced by a single moving charge to be,
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 where the vector $\vec{r}$ is still the separation vector between the location of the moving charge at a given time and the observation location at the same time -- assuming that the charge is moving much more slowly than the speed of light. Again, we cannot derive this equation, it is a model of the point charge magnetic field that fits the data/observation well. Like the electric field of a point charge, this is the starting point for magnetic fields (and, later, electromagnetism, in general). where the vector $\vec{r}$ is still the separation vector between the location of the moving charge at a given time and the observation location at the same time -- assuming that the charge is moving much more slowly than the speed of light. Again, we cannot derive this equation, it is a model of the point charge magnetic field that fits the data/observation well. Like the electric field of a point charge, this is the starting point for magnetic fields (and, later, electromagnetism, in general).
  
-{{184_notes:week11_1.png?150  }}+[{{184_notes:week11_1.png?150|Magnetic force on a moving charge in a magnetic field  }}]
  
 If another moving charge is brought into the scene, it will interact with the first moving charge through the magnetic field that the first charge generates. (It will also experience the electric force, but we often limit our discussion at first to the isolated magnetic interaction.) This push or pull that the new moving charge experiences is directly related to the cross product of the velocity of that charge and the magnetic field of the source charge. This [[184_notes:q_b_force|magnetic force]] is simply, If another moving charge is brought into the scene, it will interact with the first moving charge through the magnetic field that the first charge generates. (It will also experience the electric force, but we often limit our discussion at first to the isolated magnetic interaction.) This push or pull that the new moving charge experiences is directly related to the cross product of the velocity of that charge and the magnetic field of the source charge. This [[184_notes:q_b_force|magnetic force]] is simply,
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 ==== Collections of moving charges ==== ==== Collections of moving charges ====
-{{  184_notes:week9_5.png?300}}+[{{  184_notes:week9_5.png?300|Magnetic field from a line of charge}}]
  
 A single moving charge is certainly not the only kind of situation that we encounter. In fact, it's quite often that a collection of charges are moving -- forming a current. This collection of moving charges or really [[184_notes:b_current|current also generates a magnetic field]], and, similar to the electric field, the magnetic field obeys superposition. The basic premise is quite similar to the for electric fields, A single moving charge is certainly not the only kind of situation that we encounter. In fact, it's quite often that a collection of charges are moving -- forming a current. This collection of moving charges or really [[184_notes:b_current|current also generates a magnetic field]], and, similar to the electric field, the magnetic field obeys superposition. The basic premise is quite similar to the for electric fields,
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 ==== Effects and Applications ==== ==== Effects and Applications ====
 The fact that moving charges generate magnetic fields, that they superpose, and that other moving charges experience magnetic forces in the presence of a magnetic field result in a number of different magnetic phenomenon. Some are quite practical. Some of the most important ones are discussed below:  The fact that moving charges generate magnetic fields, that they superpose, and that other moving charges experience magnetic forces in the presence of a magnetic field result in a number of different magnetic phenomenon. Some are quite practical. Some of the most important ones are discussed below: 
-{{  184_notes:bfieldlongwire.png?200}}+[{{  184_notes:bfieldlongwire.png?200|Magnetic field around a current carrying wire}}]
  
 === Current-carrying wires === === Current-carrying wires ===
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 === Curved motion === === Curved motion ===
-{{  184_notes:week11_5.png?300}}+[{{  184_notes:week11_5.png?300|Motion of a charge moving through a magnetic field}}]
  
 Magnetic fields [[184_notes:q_path|cannot change the kinetic energy of charged particles]]. This is because the magnetic force acting on the particle is always perpendicular to motion of the particle. So magnetic fields can change the trajectory of a particle, but are not able to speed up or slow down the motion of the particle. As a result a particle moving in a uniform magnetic field subject to no other forces will execute [[184_notes:q_path|uniform circular motion]]. The direction of the orbit (clockwise vs counterclockwise) will depend on the sign of the charge, the direction of the velocity, and the direction of the magnetic field. Magnetic fields [[184_notes:q_path|cannot change the kinetic energy of charged particles]]. This is because the magnetic force acting on the particle is always perpendicular to motion of the particle. So magnetic fields can change the trajectory of a particle, but are not able to speed up or slow down the motion of the particle. As a result a particle moving in a uniform magnetic field subject to no other forces will execute [[184_notes:q_path|uniform circular motion]]. The direction of the orbit (clockwise vs counterclockwise) will depend on the sign of the charge, the direction of the velocity, and the direction of the magnetic field.
  • 184_notes/magnetic_field.txt
  • Last modified: 2021/07/06 17:31
  • by bartonmo