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Ch 16 Electric charge
16-1 through
40
Physics
Undergraduate 1
02/07/2013

Additional Physics Flashcards

 


 

Cards

Term
law of conservation of electric charge def
Definition

the net amount of electric charge produced in any process is zero


( aka if a postive charge is present then there is a negative charge nearby that is of equal magnitude)

Term

 Structure of Atom

 

Definition

1.Nucleus :

protons & neurtrons

small

massive density

+ charge

2.Electron cloud

large

very low density

 - charge

Term
What is the overall charge of an atom?
Definition
neutral
Term
 what is a Polar molecule?
Definition

 a molecule that is neutral overall,

but charge not evenly distributed


(e.g. water,

oxygen is more electronegative than hydrogen and excerts a stronger pull on the electrons).

Term
Normaly when objects are charged by rubbing, they hold their charge for a limited time and eventually return to their neutral state , what happens to the charge?
Definition

leak off to water particles in the air b/c its polar.

 

(e.g. a neg charge off a ruler goes to the postive charge of the water particles in the air)

Term
what is a Conductor?
Definition

material in which the valence electrons can move freely within the material*


(note these e- can't leave easily)


(move quickly toward + objects, repel -  objects)


e.g. metals

Term

Insulator def

Definition

Almost no charge flows

Most other materials

Term

semiconductors def

Definition
contain an intermediate amount of free moving electrons
Term
Explain how Metal objects can be charged by conduction
Definition

1.start with a neutral metal rod

2.Bring a charged metal ball(ex it's +)close so that they touch

3. metal rod acquires that (+) charge

 

 

aka it acquires a charge b/c the objects are in contact

=

leaves both objects with SAME charge

Term

Explain how Metal objects can be charged by

induction

Definition

1. start with a neutral metal rod

2.Now bring a (+) charged object close to the rod but NO touching.

3. The charges  within the rod are seperated (-)charges move to the end closest the (+) object and the other end (away from the object is now (+) charged.

 

the rod looks like:

(object) +©             ---           +++

 

 

* the charges in the rod have been seperated (no net charge created)

Term

1.induction causes an object

2.conduction causes object

Definition

1. both objects to have opposite charges. Causes the neutral object to seperate its charges(0ne end is + the other is -)

 

Object is brought close but doesn't touch.

 

2. both objects to have the same charge by   physical contact.

 

Term
Although Nonconductors CANT become charged by conduction or induction they can still  experience _______
Definition
charge seperation
Term

 the electric force between 2 charges is :

proportional to (1)

inversely proportional to (1)

Definition

1. product of the charges

↑#, ↑Electric Force


2. distance between them.

↑distance, ↓Electric Force

(aka 2 far apart objects)

Term
Coulomb’s law
Definition

an equation gives the magnitude of the force.

Term

F12 means

F21 means

Definition

 F12= the force felt by 1 caused by 2.

F21= the force felt by 2 caused by 1.

Term
Coloumbs law applies only to
Definition
point charges at REST
Term
 What is Superposition?
Definition

for multiple point charges,

the forces on each charge from every other charge can be calculated

and then added as vectors.


(aka the net force on a charge )

Term

electric field def

 

give formula to help with definition

Definition

the electric field at any point in space is defined as the force, F, excerted on a tiny positive (+)   test charge placed at that point divided by the magnitude of that test charge.

 

E= F/q

Term
 t or f: electric fields Aare added by the  Superposition principle 
Definition

true,

again the net electric field = sum of vectors

Term
how is the direction of the electric field determined?
Definition

a small positive test charge is placed in the field, the direction is determined by how  the electric field behaves.

 

(electric fields radiates away from +

goes toward - charges)

 

Term
Give  the direction of the charges on the field lines in an electric field
Definition

 Start: with a positive charge (+)

End:on a negative (-) charge.

Term
The field lines are closer together when
Definition
they are closer to the charge
Term
The field lines are farther apart when
Definition
when they are further from the charge
Term
the strength of the electric forces decreases with (1)
Definition
distance
Term
 what is an Electric dipole?
Definition

two equal charges, opposite in sign:

Term
The electric field between 2 closely spaced, oppositely charged parallel plates is always _____ 
Definition

constant

 

 

(for ex a capacitor)

Term
1. Field lines indicate the direction of the field; the field is ______ to the line.
Definition
 tangent 
 
Term

The magnitude of the field is proportional to the _______

 

(with respect to the field lines)

Definition
density of the field lines
Term
The static electric field inside a conductor is always what numerical value? Why? 
Definition

0

=

allows charges to move

Term
The net charge on a conductor is always located?
Definition
on its surface
Term

The electric field is _____to the surface of a conductor, why? 

Definition
perpendicular 
allows charges to  move
Term
what is Electric flux ?
Definition

to the total number of field lines crossing the area

(proportional relationship)

↑field lines =↑ flux

Term

what is Gauss’s Law?

Definition

The net number of field lines through the surface is proportional to:

1.the charge enclosed

2.flux

Term
what is the numerical value of the electric potential of the perpendicular bisector of the dipole?
Definition

0

b/c cos (90)=0

Term
postive test charges move in the(same/opposite) direction of the field lines.
Definition
same
Term
negative test charges move in the(same/opposite) direction of the field lines.
Definition
opposite
Term
the electrical potential energy of a system will (decrease/increase) when 2 LIKE charges move toward each other.
Definition
increases
Term
the electrical potential energy of a system will (decrease/increase) when 2 OPPOSITE charges move AWAY from  each other.
Definition

increases

 

+ -

Term
the electrical potential energy of a system will (decrease/increase) when 2 OPPOSITE charges move toward from  each other.
Definition

decreases

+-

 

(aka for visual purposes they will stick)

Term
the electrical potential energy of a system will (decrease/increase) when 2 LIKE  charges move apart.
Definition

decreases

++

(by moving apart they are reducing repulsion energy)

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