The presentation about Electric charge

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  Electric Charge and Electric Field
  
  © 2014 Pearson Education, Inc.
  

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  Contents of lesson
  Static Electricity; Electric Charge and Its Conservation
  Electric Charge in the Atom
  Insulators and Conductors
  Induced Charge; the Electroscope
  Coulomb’s Law
  Solving Problems Involving Coulomb’s Law
  and Vectors
  The Electric Field
  © 2014 Pearson Education, Inc.
  

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  continue
  Electric Field Lines
  Electric Fields and Conductors
  Electric Forces in Molecular Biology: DNA Structure and Replication
  Photocopy Machines and Computer Printers Use Electrostatics
  Gauss’s Law
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  Static Electricity; Electric Charge
  and Its Conservation
  Objects can be charged by rubbing
  © 2014 Pearson Education, Inc.
  

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  Charge comes in two types, positive and negative; like charges repel and opposite charges attract
  Static Electricity; Electric Charge
  and Its Conservation
  © 2014 Pearson Education, Inc.
  

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  Electric charge is conserved—the arithmetic sum of the total charge cannot change in any interaction.
  Static Electricity; Electric Charge
  and Its Conservation
  © 2014 Pearson Education, Inc.
  

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  Electric Charge in the Atom
  Atom:
  Nucleus (small, massive,
  positive charge)
  Electron cloud (large, very
  low density, negative
  charge)
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  Electric Charge in the Atom
  Atom is electrically neutral.
  Rubbing charges objects by moving electrons from one to the other.
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  Polar molecule: neutral overall, but charge not evenly distributed
  Electric Charge in the Atom
  © 2014 Pearson Education, Inc.
  

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  Insulators and Conductors
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  Conductor:Insulator:
  Charge flows freelyAlmost no charge flows
  MetalsMost other materials
  Some materials are semiconductors.
  
  
  

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  Induced Charge; the Electroscope
  Metal objects can be charged by conduction:
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  Induced Charge; the Electroscope
  They can also be charged
  by induction:
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  Induced Charge; the Electroscope
  © 2014 Pearson Education, Inc.
  Nonconductors won’t become charged by conduction or induction, but will experience charge separation:
  

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  Induced Charge; the Electroscope
  The electroscope can be
  used for detecting charge:
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  Induced Charge; the Electroscope
  The electroscope can be charged either by conduction or by induction.
  © 2014 Pearson Education, Inc.
  

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  Induced Charge; the Electroscope
  The charged electroscope can then be used to determine the sign of an unknown charge.
  © 2014 Pearson Education, Inc.
  

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  Coulomb’s Law
  Experiment shows that the electric force between two charges is proportional to the product of the charges
  and inversely proportional
  to the distance between
  them. Coulomb’s law in animation
  © 2014 Pearson Education, Inc.
  

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  Coulomb’s Law
  Coulomb’s law:
  
  
  This equation gives the magnitude of the force.
  © 2014 Pearson Education, Inc.
  (16-1)
  

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  Coulomb’s Law
  © 2014 Pearson Education, Inc.
  The force is along the line connecting the charges, and is attractive if the charges are opposite, and repulsive if they are the same.
  

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  Coulomb’s Law
  Unit of charge: coulomb, C
  The proportionality constant in Coulomb’s law is then:
  k = 8.988 × 109 N∙m2/C2
  Charges produced by rubbing are typically around a microcoulomb:
  1 µC = 10−6 C
  © 2014 Pearson Education, Inc.
  

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  Coulomb’s Law
  Charge on the electron:
  e = 1.602 × 10−19 C
  Electric charge is quantized in units of the electron charge.
  
  © 2014 Pearson Education, Inc.
  

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  Coulomb’s Law
  The proportionality constant k can also be written in terms of ε0, the permittivity of free space:
  © 2014 Pearson Education, Inc.
  Some examples for Coulomb’s law
  

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  Coulomb’s law strictly applies only to point charges.
  Superposition: for multiple point charges, the forces on each charge from every other charge can be calculated and then added as vectors.
  Coulomb’s Law
  © 2014 Pearson Education, Inc.
  

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  The net force on a charge is the vector sum of all the forces acting on it.
  Solving Problems Involving Coulomb’s Law and Vectors
  © 2014 Pearson Education, Inc.
  

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  Vector addition review:
  Solving Problems Involving Coulomb’s Law and Vectors
  © 2014 Pearson Education, Inc.
  

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  Electric Field Lines
  © 2014 Pearson Education, Inc.
  The electric field can be represented by field lines. These lines start on a positive charge and end on a negative charge.
  

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  Electric Field Lines
  The number of field lines starting (ending) on a positive (negative) charge is proportional to the magnitude of
  the charge.
  
  The electric field is stronger where the field lines are closer together.
  © 2014 Pearson Education, Inc.
  

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  Electric Field Lines
  Electric dipole: two equal charges, opposite in sign:
  © 2014 Pearson Education, Inc.
  

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  Electric Field Lines
  Summary of field lines:
  Field lines indicate the direction of the field; the field is tangent to the line.
  The magnitude of the field is proportional to the density of the lines.
  Field lines start on positive charges and end on negative charges; the number is proportional to the magnitude of the charge.
  © 2014 Pearson Education, Inc.
  

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  Photocopy machine:
  drum is charged positively
  image is focused on drum
  only black areas stay charged and therefore attract toner particles
  image is transferred to paper and sealed by heat
  Photocopy Machines and Computer Printers Use Electrostatics
  © 2014 Pearson Education, Inc.
  

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  Photocopy Machines and Computer Printers Use Electrostatics
  © 2014 Pearson Education, Inc.
  

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  Laser printer is similar, except a computer controls the laser intensity to form the image on the drum
  Photocopy Machines and Computer Printers Use Electrostatics
  © 2014 Pearson Education, Inc.
  

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  Summary of Chapter
  Two kinds of electric charge—positive and negative
  Charge is conserved
  Charge on electron: e = 1.602 × 10−19 C
  Conductors: electrons free to move
  Insulators: nonconductors
  © 2014 Pearson Education, Inc.
  

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  Summary of Chapter 20
  Charge is quantized in units of e
  Objects can be charged by conduction or induction
  Coulomb’s law:
  
  
  Electric field is force per unit charge:
  © 2014 Pearson Education, Inc.
  (16-3)
  (16-1)
  

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  Summary
  Shortly electric charge is…
  For the next lesson
  
  What is the electric field
  What is the Electric potential
  Electric potential energy