PHY 2049: Physics II

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PHY 2049 Physics II

• There is a proposal to move the final to Monday
  (8/4) from Wednesday (8/6). Any objections?
• To purchase Wiley Plus, the URL is
• http//he-cda.wiley.com/WileyCDA/Section/id-320351
  .html

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PHY 2049 Physics II

• About bicycle riding If some one shows you a
  trick, it means that,
• It is possible to do that trick
• The person who showed you, can do the trick
• It does not mean that you can do the trick.
• Try it a lot of times and you can too.

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PHY 2049 Physics II

• Coulombs law
• Two kinds of charges, positive and negative,
  unlike attract, like repel.
• Electrons and Protons
• q 1.602 x 10-19 C
• Current I dq/dt 1 Amp. 1 C/s
• Add forces as vectors

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PHY 2049 Physics II

• A rule
• Try to calculate the force magnitude by ignoring
  the signs of charges. Then assign the direction
  by looking at the signs.
• Never do both (using the charge signs in the
  calculation of the force and then assign the
  direction).

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PHY 2049 Physics II

• Charges are introduced
• by rubbing (depends)
• Touching (same)
• By induction (opposite)

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PHY 2049 Physics II

• Balls are touched and then separated. Rank them
  by
• Charge left
• Magnitude of Force before
• After
• Charge transferred 3,1,2

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PHY 2049 Physics II

• Force on the center charge 6kq2/d2

d
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PHY 2049 Physics II

• q1 q4 Q q2 q3 q
• what is Q/q so that the force on 1 is zero
• All charges same sign. There is no solution.
• Q and q different sign. There is a possible
  solution.
• Is the answer the same if the force on 3 is to be
  zero

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PHY 2049 Physics II

• What is the force on the central chlorine ion?
• Suppose that we put in an electron that sits on a
  cesium site and neutralizes it, which way does
  the Chlorine move?

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PHY 2049 Physics II
environment

• Electric Field
• Force F qE
• E k ? r qi/ri2

Test charge
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• Electric field lines denote direction
• Their density represents magnitude
• They do not cross

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PHY 2049 Physics II

• q1 2Q
• q2 - 2Q
• q3 -4Q
• E at origin

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PHY 2049 Physics II