Electrostatics Flashcards
how do you describe the electric field inside a charged parallel plate capacitor ?
Electric field is constant and perpendicular to the plates.
Describe the electric potential in a parallel plate capacitor ?
Electric potential increases linearly from the negative to the positive plate.
how do electric field lines point towards charges ?
Electric field lines point AWAY from positive charges, Toward negative charges.
what does voltage also signify ?
V= Potential Difference
What happens to charge and capacitance with a dielectric between isolated conductors ?
The presence of a dielectric between two isolated conductors carrying equal but opposite charges cannot change the magnitude of the separated charge, but it does INCREASES the capacitance.
What is the formula for change in Electric PE ?
change PE ^E = q x change in electric potential = qV
What is work done by electric field?
W by E = - change in Electric potential energy
What is the elementary charge (smallest possible unit) ?
e = 1.6 x 10^-19 C
What is electrostatic Force equation ?
FE = K |Q||q|/ r^2
what is value of k (dielectric constant) in electrostatics ?
k = 9 X 10^9 N x m ^2/ C^2
What is formula of electric field ?
E= Electric force/ charge (q)
E= FE/q
What is electric field from point charge ?
E = k |Q|/r^2
What is unit for electric potential ?
J/C or (Volt)
What is formula for electric potential form point charge ?
electric potential = k Q/r
What is the unit for electric charge?
Coulombs
What is unit for electric field ?
N/C (or V/m)
What is equation for capacitors (conducting surfaces separated by insulator)
C= k eo A/d
k : dielectric
Eo : characteristic of insulator
D: distance between surfaces
What is the unit for Capacitors?
C= Farads
What is formula for charge on capacitor ?
Q = CV
What is formula for energy stored by capacitor ?
PE cap= 1/2 QV= 1/2 CV^2= Q^2/2C
What is formula for electric field on a capacitor ?
V = Ed
or E= V/d
What is conductor ?
conductor: material in which charges move freely
What happens when you apply potential difference (voltage) to conductor ?
apply voltage (potential difference) allows net movement of charge (current)
What is a current in conductor ? What is formula and units for current ?
Current: flow rate of charge
I = change in Charge/ time
I = Q/t
units Amperes (A) : C/s
What is formula for Ohms’ law ?
V = IR
What is resistivity ?
resisitivity: how much a material opposes flow of charge through it
What is resistance ?
Resistance ; how much an OBJECT opposes flow of charge through it
What is formula for Resistance ? what is the unit?
R= p (resistivity) L/A
units : ohm
What is the Req equation for resistors in series ? What do resistors have in common
Req= R1 + R2 + R3….
(req series > R1, R2, R3)
resistors in series have Same CURRENT throughout
What is Req equation for resistors in parallel ? What do resistors have in common for parallel ?
Req= 1/R1 + 1/R2 + 1/R3
restores in parallel have Same VOLTAGE
what happens when you put formulas for electric field and electric potential together ?
Electric field : E = k Q/ r^2
electric potenital = k Q/r
hence together = electric potential / r
( kq/r) / (r) = same as kq/r^2
what is equation for change in KE for absence of nonconservative forces ?
Change in KE= - change in PE
What is formula for kinetic energy
KE = 1/2mv^2
What happens to voltage if two capacitors are in parallel?
. if two capacitors are in parallel, and voltages in parallel must be the same)
How do you define equilibrium for a capacitor ?
Equilibrium is established when the potential difference, or voltage, is the SAME across each capacitor
what is another formula used to calculate potential energy for capacitors?
PE =1/2QV= Q^2/2C or PE= 1/2CV^2
