CHARGES Flashcards
What is the SI unit of Charge?
Coulomb(C)
Charge cannot be created or destroyed(T/F)
True
What are insulators and Conductors?
Insulators have localized charges, do not conduct well.
Conductors distribute charges well evenly.
What is the charge for proton? electron?
proton: 1.60 x10^-19C
electron: -1.60 x10^-19C
Which one experiences faster acceleration between proton and electron and why?
electrons, due to smaller mass
What is Coulomb’s law and what does it show?
F = k(q1)(q2)/r^2
What is Coulomb’s constant(w/ units)?
k = 8.99 x 10^9 N*m^2/C^2
What other kind of “force” is analogous to Electrostatic force?
Gravitational force: Fg = Gm1m2/r^2
What is Electric field and its formula?
E is made by the source charge(Q), and can exert force on to a test charge(q), which is the charge placed in electric field. E = Fe/q = kQ/r^2
What is the difference between the two formulas: E = Fe/q and E = kQ/r^2
1st one shows how to calculate the magnitude of the electric field when an actual test charge is present and the 2nd one shows how to calculate it with only an imaginary point and not an actual charge.
What is the Electrical potential energy?
Work required to bring the test charge from infinitely far away to the particular point. Potential energy to do work by a charge related to its location.
What is the equation for Electrical potential energy and how is this equation derived?
Fe=kQq/r^2, W=Fdcos(Θ) –> W=kQq/r = dU
What does +dU mean? -dU?
\+dU = more potential energy means less stable, two like charges put together; ex. positive charge going against the electric field -dU = less potential energy means more stable, two opposite charges put together; ex. positive charge going in the same direction as the electric field.
What is Electrical Potential? Formula?
V = Potential energy per unit of charge. V = U/q
What is the difference between U and V?
U is dependent on the magnitude of the test charge because the amount of influence it experiences by the source charge’s electric field is what we are interested in.
V is not dependent on the test charge because it is solely a characteristic of the location by the source charge’s electric field.
In short, U is relative because it involves two different charges whereas V shows how much U is involved “per charge” at that specific location.
What is the formula for V when the test charge is not present?
V = kQ/r
How can dV be related to work?
Vb - Va = Wab/q
What is the tendency that charges(q) have in relation to electrical potential energy? What’s the case with positive charge(q)? negative charge(-q)?
Always towards Decreasing the U -> more stable.
dU = (-) …..W = (-)
This means: with a positive charge, dV will be negative
with a negative charge, dV will be positive.
List the formulas for: Coulomb’s law, Electrical potential energy, Electrical potential, and Electric field.
Fe = kQq/r^2 U = kQq/r E = kQ/r^2 V = kQ/r
What is Equipotential line?
Line where the Potential is the same on every point on the line, in a spherical shape.
What is electric dipole? How does it affect the V?
Measure of the separation between a positive and a negative charges that are equal, with distance “d”. The two charges will produce Electric fields and at a particular point, there will be a corresponding V value.
What is the dipole moment “p”?
p = qd(C*m)
What is the formula for electrical potential when electric dipole is present?
V = kqdcosΘ /r^2
What is perpendicular bisector of the dipole and its significance?
A plane that is perpendicular to the dipole with Θ = 90 has V = kqdcosΘ /r^2 = 0V
How do the two charges that have electric dipole behave in the external electric field?
Negative charge points opposite of E
Positive charge points same direction of E
Force is applied to both charges as E is applied and this gives “Translational Equilibrium”
what is the formula for net torque of the two charges that have electric dipole in presence of electric field?
t = pE sin(Θ )
How are magnetic fields created?
by magnets and moving charges
What is the SI unit for Magnetic field?
Tesla(T)
What are diamagnetic, paramagnetic, and ferromagnetic materials?
diamagnetic: No unpaired e-; slightly repelled
paramagnetic: some unpaired e-; weakly magnetic
ferromagnetic: some unpaired e-; strongly magnetic
What are the two types of examples that create magnetic field? Write down the appropriate equations for them.
1) Long, straight Rod
B = (u)(I)/2(pi)r
2) Circular loop wire
B = (u)(I)/2r
How to use First right hand rule to determine the I, B, and direction of B?
Thumb: direction of I
Fingers wrapping around: B(in/out of the plane)
What are magnetic forces?
Force that Magnetic field exerts on moving charges
What is Lorentz force
Sum of electrostatic force and magnetic force
What is the equation for Magnetic force experienced by a point charge? Determine what each variable means
Fb = qvBsinΘ q: charge v: magnitude of velocity B: magnitude of magnetic field Θ : angle between velocity vector and magnetic field vector.
What orientation does the charge have to be in relation to Magnetic field in order to feel Magnetic force? What happens if parallel or antiparallel?
Perpendicular to B
If parallel or antiparallel, No Fb experienced.
How to use the 2nd Right hand rule?
Velocity: thumb
Magnetic field: Fingers
Force vector for positive charge: Palm
Force vector for negative charge: Back of the hand
What is the equation for Magnetic force in a straight wire?
Fb = ILBsinΘ I: Current L: Length of wire B: magnetic field Θ : angle between L and B
