Slide 1PHY 2049: Physics IISlide 3Slide 4Phy 2049: Physics II trial runSlide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Physics IISlide 14Slide 15Slide 16Slide 17PHY 2049: Physics IICoulomb’s law: Two kinds of charges, positive and negative, unlike attract, like repel.Electrons and Protons:q = ± 1.602 x 10-19 CCurrent I = dq/dt 1 Amp. = 1 C/sAdd forces as vectorsrrqqkFˆ21221PHY 2049: Physics IIBalls are touched and then separated. Rank them by Charge leftMagnitude of Force beforeAfter Charge transferred3,1,2PHY 2049: Physics IIA ruleTry 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).Phy 2049: Physics II trial runIn Fig. at right, the particles have charges q1 = -q2 = 300 nC and q3 = -q4 = 200 nC, and distance a = 4.0 cm. What is the direction of the force on particle 4?A. B.C. D. [-0.344N, -0.218N], 212.38ºPHY 2049: Physics IIForce on the center charge = 6kq2/d2Direction: -x, 180º, dTALP: Take a look ProblemPHY 2049: Physics IIq1 = q4 = Q; q2 = q3 = qwhat is Q/q so that the force on 1 is zeroAll 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 zeroPHY 2049: Physics IIWhat 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?PHY 2049: Physics IIElectric FieldForce F = qEE = k ∑ rˆ qi/ri2environmentTest chargePHY 2049: Physics IIq1 = 2Qq2 = - 2Qq3 = -4QE at origin•Electric field lines denote direction•Their density represents magnitude•They do not crossPhysics IIPHY 2049: Physics II zRzqzkEˆ2/322PHY 2049: Physics IIInduction and charge transfer on contactForces summed as vectorsElectric fieldsPHY 2049: Physics IIPhysics II• Potentials add like
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