Just like in the electricity portion and its electric fields, magnetism has a magnetic field and a magnetic force. However, the magnetic force isnt as cut and dry as the electric force; you must use the right-hand rule to find the direction of the missing vector in a magnetic force problem (either the force, particles velocity, or the magnetic field vector). Likewise, if dealing with a negatively charged particle, you can use the left-hand rule as a way of counteracting the opposite charge and integrating it into the system. The RHR and LHR will be key elements in solving some magnetism problems, as well as bearing in mind the equations and being able to diagram what is happening in a magnetism problem.
Magnetic field strength (B) is a vector quantity. Its units are Tesla (T).
Magnet fields exert forces on moving charges proportional to the charge, the velocity, and the magnetic field strength. The magnetic force on a moving charge is always perpendicular to both the charge's velocity and the magnetic field.
The direction of the magnetic force on a moving charge is given by the right hand rule. Point the fingers of your right hand in the direction of a positive particle’s velocity. Curl your fingers inward in the direction of the magnetic field, and your thumb will point in the direction of the force on the charged particle. For a negatively charged particle, use your left hand.
A magnetic field can do no work on a moving charged particle, but it can change the particle’s direction.
A mass spectrometer bends a moving charge using the magnetic force to determine the mass of unknown charged particles.
A velocity selector utilizes a combination of magnetic and electric fields to allow a charged particle with a specific velocity to pass through in a straight line, while particles of other speeds and charges are deflected.
Moving Charges In Magnetic Fields
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
It was kind of cool here, note that MV that is the momentum of our particle.0558
You can change the radius by changing strength of the magnetic field.0573
We have talked about the magnetic force on a moving charge particle.0581
We talked about the electrical force, the Coulombic force on a charge particle.0584
You have to deal with both of these at the same time.0588
The electric field can do work on a moving charge.0591
Remember the magnetic field cannot do work on a moving charge.0594
But when you put all this together, you get what we call the Lorentz force, the total electromagnetic force on a charge particle.0596
And that is going to be the electric field component QE, there is our electric or Coulombic piece + V × B which is QV × B.0603
There is our magnetic contribution to the total force on a moving charged particle.0619
The velocity selector is a very interesting tool.0634
A charged particle in ×, the electric and magnetic fields can undergo constant velocity motion if the velocity, the magnetic field, and the electric field, are all selected perpendicular to each other.0637
If you set the velocity equal to the electric field strength ÷ the magnetic field strength, 0649
the particle can travel through the selector without any deflection whatsoever.0655
Particles with any other velocity are diverted off to the sides.0659
You put a bunch of charged particles into this machine, the only ones that are going to make it all the way out 0663
are those that have the exact velocity that you are after, equal to the electric field strength ÷ the magnetic field strength.0669
Let us take a look at this analytically for a second.0676
In order for this to happen, we had note that the electric field moving up on our particle 0678
must absolutely balance the magnetic field, the force pulling it toward the opposite direction down.0684
The electric force must equal the magnetic force which implies that QE must be equal to QV × B.0690
This book includes a comprehensive review of the key AP Physics C concepts and targeted strategies for acing every section of the exam. Additionally, the book includes two full length practice tests with full answer explanations.
The book offers a complete review of your AP course, strategies to give you the edge on test day, and plenty of practice with AP-style test questions. It includes 2 full length practice exams modeled on the real test, 3 separate plans to fit your study stle, review material updated to the most recent tests, and all the terms and concepts you need to know.