Electric charge and force
atoms typically have the same
protons and electrons
They are both the same charge
there is more attractive force than repulsive b/c distance affects this, so + is closer and bigger creating an unequal force with the - b/c is farther and smaller.
what is electric flux?
is the amount of field that goes through the area (parallel to A vector)
E.flux=E*Acos(theta)
what is EPE point charge and what is the new unit
V=(kq)/r
at infinity, EPE is zero
W=-EPE=+KE
-new unit= eV=1.602x10^-19
--good for small scale reaction instead of J
how dow dielectrics work?
cancel some electric field by rearranging charges of - and+, allowing more electric field lines, increasing the charge. it increases charge and capacitance.
-by polarizing
How to find the net charge of a group of atoms?
q=Ne
avo 6.023x10^23
what is Columbs law
electrostatic charge exerted on another point charge
-prop to the mag of charges interacting
-inver prop to distance
-mimics gravity
Gauss Law?
-net flux from a closed surface is prop to the charge enclosed.
gauss=Qenc/E0
1. what goes in and out cancel, only focus on lines inside the shape=all charges outside the surface is 0 for net flux
2. if charge is inside, flux is NOT zero
3. ANY shape or ANY size, as long as the charge is inside.
4. distance doesn't matter?
what is an equipotential surface?
the circle around a charge where the voltage is the same
Electric field or force does not work as a charge moves here, it is the same distance and perpendicular no matter where you move it.
E always points to decreasing PE
*know the equip for +vs- (two circles with a line down the middle) and +vs+(figure 8)
why are series charges the same
what are conductors and insulators?
Conductors are substances that readily conducts electric charge by allowing electrons to flow easily
Insulators conduct charge poorly by not allowing the electrons move around easily
Semi-conduct under certain circumstances
what is electric field?
exists at one point, can see effect with test point charge near it
-use positive test charge to see the direction of force (same as E)
-separates what creates the effect vs what feels the effect
work done by electric force is?
conservative, and will be delta EPE
-charge moves along Electric field liens
is EPE zero inside a conductor?
no, it is constant. e=-V/d.
if the voltage is the same, it is -0/d, E=0 no electric field
why cant you have ultimate voltage?
it polzarizes the dielect so much, it rips electrons off it turning it into a conductor.
Emax=dielect strength.
what is law of conservation of electric charge
the net electric charge of an isolated system, remains constant/conserved
this allows the transferring of electric charge from on object to another giving a positive or negative net charge
What are the rules for drawing E field lines?
1. start on + go to -
2. # of lines prop to charge
3. never cross
4. field does carry energy, lines to not
5. go perpen. to conductors
6. E field is zero at any point within a conductors (because of reverse charges, the charges on the conductor rearrange themselves, creating a backwards flow E canceling out what E goes in and what E goes out)
EPE vs PE?
electrical potential energy (J)
electric potential (V)
area and distance affect?
how much charge you can put on plates
q=C*v
because it changes the capacitor, directly affecting charge
Eletric field makes electrons
drift, and because it goes everywhere at once, you don't have to wait for an electron to travel for an object to work because all are moving
conduction- transferring charge by touching (when one charged object touches a neutral object, they transfer the same amount of charge if same size)
induction-polarizes the object to create a dipole
These two different processes gives us two different charges on an objet
What can you remember from dot charge?
A*B= AB when parrallel
-A*B=0 when perpen.
- A*B=-AB when anti parallel
eletric potentail is highest near?
+ charged plate and lowest at - charged plate, regardless of charge proton or electron
capacitor is treated like a constant, why?
c is only changes on area and distance and dielectric between plates, independent of charge and voltage.
what is a graphical representation of ohms law
linear slope