Electrostatics and Magnetism . Flashcards
What is the SI unit for charge?
Coulomb .
what is the fundamental unit charge of electrons and protons?
1.6 x 10^-19
What are conductors
they allow free and uniform passage of electrons when charged
What are insulators?
resist the movement of charge and will have localized areas of charge that do not distribute over the surface of the material
What is coulomb’s law?
gives the magnitude of the electrostatic force vector between two charges. The force vector always points along the line connecting the centers of the two charges.
Fe = kq1q2/r^2
Every charge a…?
an electric field, which can exert forces on other charges.
What is an electric field?
the ratio of force that is exerted on a test charge to the magnitude of that charge.
E = Feq = kQ/r^2
What are field lines?
representation of electric field vectors, they radiate outward form positive source charges and radiate inward to negative source charges. Positive test charges will move in the direction of field lines, negative charges go opposite.
What is the electrical potential energy?
it is the amount of work required to bring the test charge from infinitely far away to a given position in the vicinity of a source charge. It will increase when two like charges move toward each other or when two opposite charges move further apart. It will decrease when two opposite charges move toward each other or when tow like charges move further apart.
U = kQq/r
What is electrical potential?
is the electrical potential energy per unit charge. Different points in the space of an electric field surrounding a source charge will have different electrical potential values.
From electrical potential energy: V=U/q .
From source charge: V= kQ/r
What is potential difference (aka voltage)?
the change in electrical potential that accompanies the movement of a test charge from one position to another. Potential difference is a path independent and depends only on the initial and final positions of the test change. The units for both electrical potential and voltage are volts.
ΔV = Vb -Va = Wab/q
In what direction will test charges move?
spontaneously in the direction that results in decrease of their electrical potential energy. Positive test charges move from high to low potential. Negative charges move from low to high potential.
Equipotential lines
designate the set of points around a source charge or multiple source charges that have the same electrical potential. they are always perpendicular to electric field lines. work will be done when charges moves form one line to another; work is independent of the pathway. No work is done when a charge moves from a point on an equipotential line to another point on the same line.
Electric dipole
two charges of opposite sign separated by a fixed distance d generate an and electric dipole. In an external electric field, an electric dipole will experience a net torque until it is aligned with the electric field vector. the field will no induce any translational motion in the dipole regardless of its orientation with respect to the e field vector.
Magnetic fields
created by magnets and moving charges. Th SI unit is the tesla.
Diamagnetic materials
possess no unpaired electrons and are slightly repelled by a magnet.
Paramagnetic materials
possess some unpaired electrons and become weakly magnetic in an external magnetic field.
Ferromagnetic materials
possess some unpaired electrons and become strongly magnetic in an external magnetic field.
Poles of magnets .
has a North and south, Field line point from north to south.
magnetic fields in wires
create magnetic field that are concentric circles around the wire.
External magnetic fields
exert forces on charges moving in any direction except parallel or antiparallel to the field.
Point charges and circular motion
may undergo uniform circular motion in a uniform magnetic field wherein the centripetal force is the magnetic force acting on the point charge.
How is the direction of magnetic force on a moving charge or current carrying wire determined?
by using the right hand rule
What is the Lorentz force?
is the sum of the electrostatic and magnetic forces acting on a body,
Electrical potential near a dipole
V=kqd/r^2 cosΘ
Dipole moment equation
p=qd
Electric field on the perpendicular bisector of a dipole
E =1/4πe0 x P/r^3
torque on a dipole in an electric field
t= pE sin Θ
Magnetic field from a straight wire
B= u0I/2πr
Magnetic field from a loop of wire
Bu0I/2r
Magnetic force on a moving point charge
Fb = qvBsin Θ
Magnetic force on a current-carrying wire
FbILBsin Θ
consta k is
Coulomb’s constant/ electrostatic constant
1/4πe0 = 8.99 x 10^9 N m^2/C^2 .
What is e0
permittivity of free space
8.85 x 10^-12 C^2/N m^2
What is variable Q
source charge which actually creates the field
what is q
the test charge, charge placed in electric field.
what is u0
Permeability of free space
4π x 10^ -7
right hand rule
thumb- velocity and direction of flow
fingers-field lines
palm- positive force
back hand- negative force
