Chapter 27

Question 1

What does the size of the force on a moving charge in a uniform magnetic field depend on

Answer 1

Magnetic flux density
Charge Q on the particle
Speed v of the particle

Question 2

Mag force on a moving charge

Answer 2

F = BQv 
F = BQvsin(theta) 
Derive: 
F=BIL; I= Q/t 
F=BQL/t; v=L/t
F=BQv; Q=e 
F=Bev

Question 3

Radius of orbiting charges

Answer 3

Centripetal force = magnetic force on a moving charge
Mv^2/r = Bev
r= mv/Be; mv= momentum

Question 4

Charge-to-mass ratio of an electron

Answer 4

Also known as specific charge on the electron, ‘specific’= per unit mass 
Electron traveling in a circle 
e/Me = v/Br 
eVca = 1/2(Mev^2); r=Mev/Be 
e/Me = 2Vca/r^2B^2

Question 5

Electron beam is straight

Answer 5

Electric force = magnetic force
eE=Bev
v=E/B; E= V/d
v= V/Bd

Question 6

Velocity selector

Answer 6

Velocity
Higher: F= BQv, mag force is stronger, electric force weaker,
Lower: mag force weaker, electric force stronger

Question 7

Hall effect

Answer 7

Mechanism mag forces = electric forces
Probe is semiconductor, electrons travel faster giving it a greater effect
Small current flows through probe and a mag field is applied pushing electrons to one side by mag force accumulating on one side and creating a small voltage
Greater flux density, greater hall voltage
Mag field direction is reversed, electrons pushed to other side, hall voltage reversed

Question 8

Hall voltage equation

Answer 8

E = Vh/d; drift velocity, experiences force to left, BQv, force to the right, Eq
BQv = Ee 
eVh/d = Bev; v = drift velocity, I = nAve 
eVh/d = BeI/nAe 
Vh= BId/nAe; A = d x t 
Vh = BI/nte; e = q(charge of individual charge carrier) 
Vh = BI/ntq

Question 9

Properties that affect radius

Answer 9

Bigger if faster and heavier( direct prop)

Smaller if stronger field( inverse B)