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Tipler Physics Ch 26
Magnetic Field
18
Physics
Undergraduate 2
05/26/2008

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Cards

Term
Force on a moving charged particle
Definition

F = qv x B = qvBsinΘ, where theta is the angle between the velocity V and field B

Term
What are the units of a tesla?
Definition
1 T = 1 N/(C m/s) = 1 N/(A m)
Term
What is a Gauss?
Definition
1 G = 10-4 T
Term
If the velocity vector of a positive charge is in the +x direction, and the B field is in the -Y direction, which direction is F?
Definition
-Z direction, according to the right hand rule
Term
If the velocity vector of a negative charge is in the +x direction, and the B field is in the -Y direction, which direction is F?
Definition

+ Z.  The RHR dictates that the force will be in the -Z direction, but because the charge is negative,

F=qV x B

the force is in the negative direction of the RHR

Term
What is the magnetic force on a straight segment of current-carrying wire?
Definition
F = IL x B
Term

What is the magnetic force on a current element?

Definition

dF = I dl x B

Term

What is a cyclotron period?

Definition
T = 2 pi m/(qB)
Term
What is a cyclotron frequency?
Definition
f = 1/T = qB/(2 pi m)
Term
What is the velocity selector?
Definition

v = E/B

 

It is set up as two capacitor plates with a constant electric field between them.  The E field is perpendicular to a B field.  If a particle is moving at a certain velocity, the E field will balance out the B field that is created by the particle.  Only a charge of that velocity can move through the capacitors undeflected

Term

What is the magnitude of torque on a rectangular current loop?

Definition

τ = NIABsinΘ

Where N = the number of loops

I=current

A = area enclosed by loop

B = B field

sinΘ =  angle between B field and the orientation of the loop 'n' (found by RHR, fingers curl around direction of I, thumb points to n)

Term
What is the magnetic dipole moment of a current loop?
Definition

μ = NIAn

N = number of loops

I = current

A = area

n = see card 11

Term
What is the torque on a current loop?
Definition

τ = μ x B

All vector units

Term
What is the potential energy of a magnetic dipole?
Definition
U = -μBcosΘ
Term
What is the Hall effect?
Definition
When charges are traveling in a conducting wire in a B field perpendicular to their velocity, charges will be pushed to one side because of the force the B field exerts on them.  The separation of charge is the Hall effect
Term
What is the Hall voltage?
Definition

VH = EH ω = vd

ω = width of the strip that the potential difference is being measured. 

Vd = drift velocity of electrons in a wire

EH = the electric field created by the separation of charges

Term
Why is there a Hall voltage?
Definition
A Hall voltage exists because when a magnetic field pushes like charges to one end of a wire or strip, there is a difference in voltage between the top of the wire, which holds one type of charge, and the bottom of the wire, which holds the opposite charge.  This difference in charge can be measured
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