PHYS 272 Lecture Notes - Lecture 1: Electronvolt, Circular Motion, Drift Velocity

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sangriabat66

30 Jul 2018

School

University of Maryland

Department

Physics

Course

PHYS 272

Professor

any

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Document Summary

F = q (v x b), where force is perpendicular to b and current i (no force if the charge is not moving as v = 0) Fmag r q > 0 (clockwise) q < 0 (anticlockwise) Both forces are equal, hence (cid:2923)v2(cid:2928) = q v b or r = (cid:2923)v(cid:2927)b. Time taken for 1 circle = (cid:2870) v = (cid:2870) (cid:2923)(cid:2927)b (we can see this is independent of r or v) Frequency f = (cid:2869)t = (cid:2927)b(cid:2870) (cid:2923) (known as cyclotron frequency) Lorentz force f =f(cid:2915)(cid:2922)(cid:2915)(cid:2913)+f(cid:2923)a(cid:2917)=qe+qvb component gives circular motion (spiral or helical) Motion under e and b is crossed and happens naturally due to hall effect. Electrons keep moving towards current (current) evdrift b = fmag = e eh = felect (vdrift = drift velocity, eh * hall voltage) Hall effect, but charge carries positive (vs electrons larlier)

Related Questions

Two positivecharges (+Q = 1.00 microcoulombs) are heldin position at +,-2.25 centimeters along the x-axis, as shown in the diagram. A thirdpositive charge (+q = 0.05 microcoulombs and m= 6.5micro-kilograms) is free to move along thex-axis.

The magnitude of force between pairs ofcharges is given by F(Q1,Q2)=kQ1Q2/r^2, where the constant k is8.99x10^9 N*(m^2)/(Coulombs^2), Q1 and Q2 are the electric chargesgiven in Coulombs, and r is the distance between Q1 and Q2 given inmeters. Note that when both forces are positive, the forcebetween them is repulsive.

A)Is the motion of the small charge, q, an example of simple harmonicoscillation? Carefully explain why or why not.

B)Assume q<<Q Find the time for q to complete oneoscillation.

A student wants to check the resistance of a resistor by measuring the voltage across it (V) and the resulting current through it (I) and then calculating the resistance R=V/I. He measures four different values of V and the corresponding currents I, as follows: Voltage, V (volts): 11.2 13.4 15.1 17.7 Current, I (amps): 4.67 5.46 6.28 7.22 A) Calculate the four corresponding values of R (which will come out in ohms). What is his best estimate for R, and what is the random component of its uncertainty (deltaRrandom)? B)The resistor is rated at 2.50 ohms, which does not lie within the range Rbest + or - deltaRrandom, so he considers the possibility that the voltmeter and ammeter suffer some systematic error. The lab technician states that many of the meters in the lab have up to a 2 percent systematic error. Use error propagation to find the possible systematic error in R, and then combine the systematic and random errors to give the total uncertainty. (In both calculations, combine errors in quadrature.) What is his final answer and how does it compare with the given value?

A block having mass m and charge +Q is connected to aninsulating spring having a force constant k. The block lies on africtionless, insulating, horizontal track, and the system isimmersed in a uniform electric field of magnitude E directed asshown in the figure below. The block is released from rest when thespring is unstretched (at x = 0). We wish to show that the ensuingmotion of the block is simple harmonic. http://www.webassign.net/serpse8/25-p-008.gif (b) What kinds of potential energy exist withinthis system? (Select all that apply.) kinetic energy gravitational potential energy elasticpotential energy electrical potential energy c) Consider the instant the block is released fromrest to be the initial configuration of the system. The finalconfiguration is when the block momentarily comes to rest again.What is the value of x when the block comes to rest momentarily?(Use any variable or symbol stated above along with the followingas necessary: π.) x= d)What is the value of x0?(Use any variable or symbol stated above along with the followingas necessary: π.)
x0=
e) Define a new coordinate system x'such that x' = x− x0. Showthat x' satisfies a differential equation forsimple harmonic motion.
f) Find the period of the simple harmonic motion. (Use anyvariable or symbol stated above along with the following asnecessary: π.)
T=
g) How does the period depend on the electric fieldmagnitude?

PHYS 272 Lecture Notes - Lecture 1: Electronvolt, Circular Motion, Drift Velocity

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