Electrostatics and Magnetism Flashcards
fundamental unit of charge (e); charge of protons and electrons (but positive and negative)
e = 1.60 x 10^-19 C (coulomb)
quantifies magnitude of electrostatic force between two charges
Coulomb’s law
Coulomb’s law
F(e) = (k q1 q2) / r^2
where:
k = Coulomb’s constant (8.99 x 10^9 N*m^2/C^2)
q1 and q2 = magnitude of charges
r = distance between charges
Coulomb’s constant (k)
k = 8.99 x 10^9 N*m^2/C^2
generated by every charge, and exert force on other charges
electric field
electric field (E)
E = F(e) / q = kQ / r^2
where:
q = test charge
Q = source charge
F(e) = magnitude of force felt by point charge
k = Coulomb’s constant (8.99 x 10^9 N*m^2/C^2)
r = distance between charges
used to represent electric field vectors for a charge; point away from a positive charge and point toward a negative charge the denser the line, the stronger the field
field lines
the work necessary to move a test charge from infinity to a point in space in an electric field surrounding a source charge; if like charges, then U will be positive; if unlike charges, then U will be negative
electric potential energy (U)
electric potential energy (U)
U = kQq / r
where: k = Coulomb's constant (8.99 x 10^9 N*m^2/C^2) Q = source charge q = test charge r = distance between charges
ratio of electric potential energy per unit charge, measured in volts (V)
electric potential (V)
electric potential (V)
V = U / q = kQ / r
where:
k = Coulomb’s constant (8.99 x 10^9 N*m^2/C^2)
Q = source charge
r = distance between charges
essential electrostatic equations and derivations:
where:
k = Coulomb’s constant (8.99 x 10^9 N*m^2/C^2)
the change in electric potential that accompanies the movement of a test charge from one position to another
potential difference (voltage)
potential difference (voltage)
∆V = V(b) - V(a) = W(ab) / q
where:
W(ab) = work needed to move a test charge q through an electric field from point a to b
designate the set of points around a source charge or multiple source charges that have the same electric potential; always perpendicular to electric field lines
equipotential line
as a charge is moved from one equipotential line to another work is ____ (done/not done)
work is done
as a charge is moved along the same equipotential line work is ____ (done/not done)
work is not done
generated when two charges with opposite signs are separated by a fixed distance (d); in an electric field, will experience a net torque until it aligns with the electric field vector
electric dipole
the product of charge and separation distance
dipole moment (p)
dipole moment (p)
p = qd
where:
q = test charge
d = separation distance
net torque on a dipole (𝜏)
𝜏 = pE sin θ
where:
p = magnitude of dipole moment
E = magnitude of uniform external electric field
θ = angle the dipole moment makes with the electric field
created by magnets and moving charges; SI unit is tesla (T; 1T = 1000 gauss)
magnetic field
possess no unpaired electrons and are slightly repelled by magnet
diamagnetic materials
possess some unpaired electrons and become weakly magnetic in an external magnetic field
paramagnetic materials
possess some unpaired electrons and become strongly magnetic in an external magnetic field
ferromagnetic materials
magnetic field at distance r from a wire (B)
B = μ(o)*I / 2πr
where:
μ(o) = permeability of free space
I = current through wire
permeability of free space (μ(o))
μ(o) = 4π x 10^-7 T*m/A
sum of electrostatic and magnetic forces acting on a body
Lorentz force
may be exerted on a charge when it moves in a magnetic field
magnetic force (F(B))
magnetic force (F(B))
F(B) = qvB sin θ
where:
v = magnitude of velocity
B = magnitude of magnetic field
θ = smallest angle between velocity and magnetic field vectors (v and B)
for a straight wire, magnitude of force created by external magnetic field (F(B))
F(B) = ILB sin θ
where:
I = current
L = length of wire in field
θ = angle between L and B
