Magnetism Flashcards
What is the Lorentz Force?
Magnetic forces always act perpendicular to the direction of the motion of the charged particles.
What is the Lorentz Force Law?
𝐅 = 𝑞 (𝐯 × 𝐁)
What is the Hall effect?
- The Hall effect is the production of a potential difference (the Hall voltage) across an electrical conductor
- that is transverse to an electric current in the conductor
- and to an applied magnetic field
- perpendicular to the current.
Give the parameters for the equation:
I = NevA
I = Current
N = Number of electrons per unit volume
e = Electronic charge
v = Drift velocity
A = Cross-sectional area of the bar
For Fleming’s left hand rule, state what each finger represents.
ThuMb = Motion / Force
First = Magnetic Field
SeCond = Current
What is the right hand curl rule for finding the direction of vector S for a current loop?
Thumb = S
Fingers = I
Explain why ε0 is known as permittivity of free space.
In vacuum, there are no molecules to be polarized, so 𝜀0 is called permittivity of vacuum of free space.
What is the magnetic dipole moment?
m = I x S
Where:
m = magnetic dipole moment
I = current
S = direction of wire
What are the units for the magnetic dipole moment?
A m^2
How could you find the direction of the magnetic dipole moment?
Fleming’s right hand rule.
What is the right hand curl rule for finding the direction of the magnetic field caused by a current in a wire?
Thumb = I
Fingers = B
What is µ0?
µ0 is the vacuum permeability
What is the value of µ0?
µ0 = 4π x 10^-7
What are paramagnetic materials?
Paramagnetic substances have a weak magnetism resulting from the presence of atoms (or ions) that have permanent magnetic moments.
What happens to the magnetic field of a solenoid if a paramagnetic material is placed inside?
Its atomic moments line up with the field.
The magnetic field has a small increase.
What are diamagnetic materials?
Diamagnetic materials have no magnetism.
E.g. water, wood, etc
What happens to the magnetic field of a solenoid if a diamagnetic material is placed inside?
A weak magnetic moment is induced in the direction opposite to the magnetic field of the solenoid.
The magnetic field has a small decrease.
What are ferromagnetic materials?
Ferromagnetic substances contain permanent atomic magnetic moments.
What happens to the magnetic field of a solenoid if a ferromagnetic material is placed inside?
The permanent magnetic moments align parallel to each other in the direction of the solenoid’s magnetic field.
The magnetic field has a large increase.
Explain how the magnitude of a magnetic field are represented by magnetic field lines.
The number of magnetic field lines per unit area (density of field lines) represents the magnitude.
Explain how the direction of a magnetic field are represented by magnetic field lines.
The arrows on the field lines show the direction of the magnetic field.
What is Farday’s Law of Induction?
ε = - dΦ(B) / dt
Where:
ε = induced voltage
dΦ(B) = change in magnetic flux
dt = change in time
What is the magnetic flux through a solenoid?
Φ = (total number of turns) x (area of solenoid turn) x (magnetic field)
Φ = (NL) (πr^2) (B)
Where L is the self inductance
What is the magnetic flux through a surface?
Φ(B) = ∫ B * dA
What is the equation for a magnetic field due to a current-carrying wire at a distance r away?
B = µ0 I / 2πr
What is the equation for angular frequency?
ω = 2π / T = v / r
What is the equation for centripetal force?
F = mv^2 / r
What is the equation to find the force per unit length between two wires?
F / ΔL = (µ0 I(1) I(2)) / (2πr^2)
