# Shared Flashcard Set

## Details

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

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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