Electrostatics and Magnetism Flashcards
What is electrostatics?
the study of stationary charges and the forces that are created by and which act upon these charges
What is grounding?
the act of returning charge to the earth
What is the coulomb?
fundamental unit of charge
e = 1.60x10-19 C
What is the charge of a proton and electron
1 C each but protons are positive, electrons negative
What is an insulator?
an object that will not easily distribute a charge over its surface and will not transfer that charge to another neural object very well
What is a conductor?
an object where the charges will distribute evenly on the surface and can transfer charges well
What is Coulomb’s Law?
Fe = kq1q2/r^2 Fe = magnitude of the electrostatic force k = Coulomb's constant = 8.99 x 10^9 q1/q2 = magnitudes of the charges r = distance between the charges
What is the electric fields?
fields exert forces on other charges that move through their space
Test charge vs source charge
Test charge (q) - the charge placed in the electric field Source charge (Q) - the charge creating the electric field
What is the equation for calculating an electric field?
E = Fe/q = kQ/r^2 E = electric field magnitude in N/C Fe = magnitude of the force felt by the test charge q k = electrostatic/Coulomb's constant Q = source charge magnitude r = distance between charges
What are field lines?
imaginary lines that represent how a positive test charge would move in the presence of the source charge
What is electric potential energy?
stored energy that comes from the relative position of one charge with respect to another charge, or collection of charges
What is the electric potential energy equation?
U = kQq/r U = electric potential energy k = electrostatic/Coulomb's constant Q = source charge magnitude q = test charge magnitude r = distance like charge will produce positive U and unlike charges are -U
What change in potential energy would make a system for stable?
A decrease so 5 J —> 2J or -4 J —> -7 J
What is electric potential and its equation?
the ratio of the magnitude of a charge's electric potential energy to the magnitude of the charge itself V = U/q = kQ/r V = electric potential in volts (J/C) U = potential energy q = test charge k = coulombs constant Q = source charge r = distance
What potential difference and it’s equation?
the difference between electric potentials at two points, aka voltage
deltaV = Vb - Va = Wab / q
Wab = work needed to move a test charge q through an electric field from point a to point b
What is an equipotential line?
a line on which the potential at every point is the same
What is an electric dipole?
a molecule that results from two equal and opposite charges being separated by a small distance d from each other
What is the equation for dipole moment?
p = qd p = dipole moment
Equation for electric potential of a dipole
V = kqd/r^2 * costheta
What is the perpendicular bisector of the dipole?
an important equipotential line to be aware of is the plane that lines halfway between +q and -q
What is the equation for the magnitude of an electric field on a perpendicular bisector?
E = k x p/r^3
Equation for torque of the dipole
T = pEsintheta
What is a magnetic field?
a field that can act on charges and was created by a moving charge
What is the unit for magnetic field strength?
Tesla (T) = Ns/mC
What are diamagnetic materials?
material made of atoms with no unpaired electrons and have no net magnetic field
What are paramagnetic materials?
material made of atom that have unpaired electrons and a magnetic dipole moment; become weakly magnetized in presence of an external magnetic field; Al, Cu, Au
What are ferromagnetic materials?
material made of atom that have unpaired electrons and a magnetic dipole moment; become strongly magnetized when exposed to an external magnetic field; iron, nickel, cobalt
What is the equation for the magnetic field of a long straight wire?
B = mu0I/2pir B = magnetic field r = distance of the magnetic field from the wire mu0 = 4pi x 10^-7 I = current
What is the equation for the magnetic field of a circular wire loop?
B = mu0I/2r B = magnetic field r = distance of the magnetic field from the wire mu0 = 4pi x 10^-7 I = current
What is Lorentz force?
sum of electrostatic and magnetic forces
What is the equation for magnetic force?
F(subB) = qvBsintheta
What is the equation for magnetic force on a straight wire?
F(subB) = ILBsintheta
