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					Question of the Day

        TAKS
   5 weeks (15 days)
                                #25




The graph shows how the momentum of a
given mass changes during a period of
motion. According to the information, what is
the momentum in kg●m/s at 2.75 seconds?
Record your answer.
                                        #26



                             If the trend continues, what
                             is the most likely voltage
                             needed to maintain a 1.5-
The graph shows how the      amp current through 80
                             meters of the wire?
voltage needed to maintain
                             F 10 volts
a constant current of 1.5
                             G 18 volts
amps through a wire
conductor varies with the    H 250 volts
length of the wire.          J 400 volts
                   #27
What is the net force exerted on a 90.0 kg
race-car driver while the race car is
accelerating from 0 to 44.7 m/s in 4.50 s?
F 9.8 N
G 20 N
H 201 N
J 894 N
                   #28
Which of these elements is most likely to
donate one electron?
F Be
G Cs
H Rn
J He
Electrostatics

  Chapter 17
        Components of Atom
• Electrons
  – Negative charge
  – All are created alike
  – Located outside nucleus in electron cloud
• Protons
  – Positive charge
  – 2000 times mass of electron
  – Charge equal and opposite to
    electron
  – Located in nucleus
• Neutrons
  – No charge
  – Located in nucleus
           More about Atoms
• Contain equal amounts of electrons and protons
• Net charge of atom is zero
• Protons and neutrons are relatively fixed in
  nucleus
• Electrons may be transferred from one atom to
  another
  – Inner electrons are held tightly
  – Outer electrons are held loosely
  – Charges result from transfer of electrons
• Ions are atoms that gain or lose electrons are
           Transfer of Charges
• The SI unit for charge – Coulomb
   – Electron - -1.60 x 10-19C
   – Proton - + 1.60 x 10-19C
• Like charges repel and unlike charge attract
• Law of Conservation of Charge
   – Charges can be neither created nor destroyed
   – The number of electrons gained by one is equal to the
     number of electrons lost by another
• Conductor – free electrons
• Insulators – electrons held tightly
          Methods of Charging
• Friction
   – Electrons are transferred by rubbing two materials
• Contact
   – Electrons are transferred by direct contact
• Induction
   – Electrons are caused to gather or disperse by the
     presence of nearby charge (no contact)
   – Occurs in conductors
• Polarization
   – Similar to induction but occurs in insulators
             Electric Forces
• Electrical forces arise because of the way
  charges are either repelled or attracted.
• Coulomb’s Law
  – Similar to Newton’s law of gravity
     Fg = G m1 m2          G=
              d2
  – The electric force between two charge objects
    is proportional to the product of the charges
    and inversely proportional to the square of the
    distance that separates them.
      Fe = kc q1q2         kc =
               r2
Gravitational Force vs Electric Force
•   Type of force
•   Attractive vs repulsive
•   Calculations
•   Constants
•   Comparison of forces with charges –
    Sample Problem 17A

				
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