AP PHYSICS 2 - UNIT 10: ELECTROSTATICS

What happens if a positively charged metal sphere is brought near an uncharged one but doesnt touch it?

electrons in the uncharged sphere go towards the positively charged sphere (opposites attract) and protons to the other side, becomes polarized

What does polarization mean in the context of electrostatics?

electrons to one side, protons to the other

What happens when an equally sized positive metal sphere touches an equally sized uncharged one?

They both end up with Q/2 and are positively charged

Once a particle moves out of a magnetic field, what direction does it go in?

straight line

is an electric potential a VECTOR or a SCALAR

SCALAR

What is total electric potential ENERGY in a system of charges?

The sum of the potential energies between each pair, kqq/r for each pair

if there's 3 charges in a triangle, how would you know the total electric potential ENERGY of the system?

use kqq/r for each pair, signs matter

Electric potential energy is positive IF

both charges are the same sign(repulsion)

Electric potential energy is negative IF

the charges have opposite signs(attraction)

How to find the electric potential at a point between two charges on a line?

calculate the potential from both charges and just add them (because potential is scalar).

How do you find the electric potential at a certain point due to the prescense of multiple objects?

1. Find the distances from the point to each object

2. Use kq/r for each object

3. Add up the potentials (because its a scalar)

4. Signs matter

Is electric FIELD a VECTOR or a SCALAR?

VECTOR

Electric field lines point towards..

decreasing potential

Protons travel in

the same direction as electric field lines

"k" in electrostatics equal to

Coulombs constant NOT bolztmanns!!!!

Total electric POTENTIAL at a certain point is

Coloumbs constant k times (the added charges over the added distances to the point)

How to find the electric field at a certain location point charges

do kq/r^2 for each charge, then add them together as vectors(keep in mind x and y components)

Electric FIELD / Electric FORCE between two charges

kqq/r^2

Electric potential energy

kqq/r

The capacitance of a capacitor can be increased by

bringing the plates closer

electric field strength of a parallel-plate capacitor depends only on

the charge and the area (e = v/r)

what do you need to keep in mind when talking about electrons?

their charges and mass

when an external force moves a positive particle Y to a positive particle X but doesn't touch, what work is done?

work is done by an external force, because it is pushing naturally repelling things together

when a positive particle is moved towards a negative particle X but doesn't touch, what work is done?

work is done by the electric field

in the equation for the electric field, kq/r^2, what does q and r refer to?

q refers to the charge that is creating the electric field. r refers to the distance between the charge creating the field, and the point where you are determining the strength.

the electric potential is not a vector, it's just a number that is either ___ or ___

positive or negative

How to find electric potential at a certain point?

plug in plus and minuses for the charges into kq/r and add up all the charges

positive charge will always create a __ electric potential

positive

Negative electric potential just means

its a negative number, no direction

For electric force, even if one charge is very big and one is very small, they will still exert

equal and opposite forces on each other

The force on a positive charge points ___ the direction of the electric field

in the same

The force on a negative charge points ___ the direction of the electric field

in the opposite

If you don't know the location of every single point charge, you can't find

electric force

if two parallel plates force's are in the same direction(aka they are opposite charges), their forces exerted on a charge in between them

add together

electric field between parallel plates is always ___, meaning that

uniform, same strength and direction at every point between the plates

what is the force exerted by the electric field in between two parallel plates ALWAYS?

the same

If two spheres, one charged and one uncharged, are touching, what happens to them?

they act as one conducter, electrons can go in beetween them

What happens when two spheres are touching versus when they're just near each other?

touching: charges move between them, can leave permanently charged

Not touching: charges just rearrange, no permanent cjarge

what happens when you move spheres that are touching far away from each other

their charge gets locked in and stays permanent, cause they're no longer touching and can't share electrons3

what happens when two equal and opposite charged spheres touch each other?

the charges redistribute and they become nuetral

how to determine the charge on two spheres after touching?

minus the smaller one from the bigger one then divide it by 2

negative charge flows towards...

increasing potential

more negative(larger sphere) =

lower potential

no flow of charge =

no difference in potential

electric field lines point ___ from positive charges

away

how would you find the net electric field at a certain point due to two charges?

e-field lines point AWAY from positive charges and TOWARD negative charges. Draw the VECTORS (broken into components)

as long as a battery is connected to a parallel-plate capcacitor, the potential difference between the plates

is constant

charge (Q) of a parallel-plate capacitor is constant when

the battery is disconnected

The electric force on a negatively charged object is ____ the electric field,

opposite

If a source charge Q is positive, what is the electric potential created by it?

positive

when a rod has been moved near(induction) to a GROUNDED electroscope, what happens to the charge in the electroscope?

Its opposite of the charge in the rod

when moving a charge from very far away to a system of point charges, how do you know what the sign of the work is?

The field and you do positive work if the charges attract. The field does negative work and you do positive work if the charges repel.

when moving a charge from very far away to a system of point charges, what happens to the potential energy?

it becomes MORE NEGATIVE if the charges are attractive

A negative charge loses potential energy when

the system becomes more stable, like when a positive charge is near a negative one

Is the potential energy between two attracting charges high or low

low

potential energy is negative when

two charges are ATTRACtiNG each other