Phys._219_Lec.09._2012.

Phys._219_Lec.09._2012. - Lecture 9-1 Lorentz Force Let E...

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Lecture 9 Lecture 9 -1 Lorentz Force Let denote the electric and magnetic vector fields. The force acting on a point charge q, moving with velocity fields is: and EB GG F G in the superimosed vE B + G G G { } F qE v B = G G This is called the Lorentz force equation. Velocity Selector Assume that the electric field is created by a parallel plate capacitor pointing along the Y axis and the magnetic field along the Z axis as shown in the figure below. Since the moving charged particle is negative: E G B G (up) (down) E y B y Fq E v B =+ =−
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Lecture 9 Lecture 9 -2 When the electric and magnetic forces balance 0 qE qvB E v B = = X Y
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Lecture 9 Lecture 9 -3 Magnetic Mass spectrometer When an ion of unknown mass enters the homogeneous magnetic field of the Magnetic spectrometer it executes a circular path. The measured radius of the circle depends on its mass m and its velocity . Thus v also has to be measured. (See Lec.8, page 12) B G B G v G
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Lecture 9 Lecture 9 -4 Physics 219 – Question 1 – February 08, 2012. a) Increase E b) Increase B c) Turn B off d) Turn E off e) Nothing A proton (charge +e) comes horizontally into a region of perpendicularly crossed, uniform E and B fields as shown. In this region, it deflects upward as shown. What can you do to change the path so it remains horizontal through the region? e +
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Lecture 9 Lecture 9 -5 Magnetic Force on a Current • Consider a straight current-carrying wire in the presence of a magnetic field B . • There will be a force on each of the charges moving in the wire. What will be the total force F on a length L of the wire? • Current is made up of n charges/volume , each carrying charge q < 0 and moving with velocity v d through a wire of cross-section A .
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Phys._219_Lec.09._2012. - Lecture 9-1 Lorentz Force Let E...

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