Class 5 Flashcards
What is Coulomb’s Law?
Fe = k Qq/r^2 where k = 9x10^9
Can Fe (electrostatic force) be attractive or repulsive?
Yes
Fe = ?
qE
A positive charge experiences force in the _______ direction as the electric field, E
same
A negative charge experiences force in the _______ direction as the electric field, E
opposite
Electric field at a point distance r away from a source charge: E = ?
k Q/r^2
Electric field points _____ from a positive charge and _____ a negative charge.
pos. charge = away from neg. charge = towards
Strength of the electric field corresponds to the ________ of field lines.
Density
How does the electric field and electric field lines relate?
The electric field at any point is tangent to the field line.
What are the units for electric potential?
J/C = V
What does change in electrical potential equal?
delta PEe = q(delta)phi = qV
How do you calculate work done by electric potential?
W by e = -(delta)PEe
Positive charges want to accelerate to regions of ______ electric potential
Lower
Negative charges want to accelerate to regions of ________ electric potential
Higher
What are capacitors?
Two conducting surfaces separated by an insulator (dielectric) that can store charge and energy.
Capacitance (C) = ?
C = kappaEo A/d Eo = constant kappa = dielectric number which is a characteristic of different insulators
What are the units of capacitance?
Farads, F
In diagrams of batteries (two lines), which line is the positive terminal?
The longer of the two lines.
When connected to a battery in a closed circuit, a capacitor will store charge: Q = ?
Q = CV
How do you calculate the uniform electric field created between charges on capacitor plates?
E = V/d
When a capacitor is charged, it is also storing energy: PEcap = ? = ? = ?
PEcap = 1/2QV = 1/2CV^2 = Q^2/2C
How do you determine the stored energy in a capacitor using a Q vs V graph?
PE = area under curve
What does a dielectric do and how does it affect capacitance (numerically)?
Increases capacitance according to its dielectric number, kappa: C = kappaC0
