Electric Force and Electric Field

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$a) What force does Trask exert on Butch? F - ^\ ~\â¢ *$

advantageoRFigure 1Here R is a unit vector directed along the line connecting the two point charges. The forcelaw, known as Coulomb's law, also describes the force between two spherical charges whereR is the distance between the centers of the two charges.Three charges are arranged along the x-axis: +3 fiC at the origin, —2 /iC atx = —2 m, and —4 /iC at x = +3 m. Find the net force on the charge at theorigin (figure 2).(-2,0) (0,0) (3,0)-4fiCF_ 2-»3F-4+3Figure 2The +3 juC charge will experience a force in the —x direction due to the — 2//C.The magnitude of this force is= 9 X_ l37 x 10-2The +3/*C charge will experience a force in the +x direction due to the — AftC.The magnitude of this force is= 9 XThe net force will point in the —x direction and have a magnitude equal tothe difference of the two contributions.netF= 1.5 X 10"3NChapter 10
Physics B ReviewBecause both charges and vector components can carry a minus sign, it's easy to make signerrors in calculating electric forces. To guard against that, use the process from the example.First, find the magnitude of the force contribution, which is always positive, and then useyour diagram to combine the different contributions with the correct signs.Electric Field •How is it that two charges separated by a distance can exert forces on each other? How doesone charge know about the presence of the other? The answer lies in the field concept. Eachcharge creates an electric field in the space surrounding it. Another charge placed at somepoint will experience the field created by the first charge at that point. But the field at thatpoint exists whether a charge is there to experience it or not. The electric field created by adistribution of charges is defined in terms of the force that a test charge would experience ifit were placed at some point. A test charge is defined as a positive charge that's so small thatits presence doesn't change the original charge distribution. Specifically, that isr.fitThe SI units for electric field are -£k When an electric field is created solely by charges at rest,it's called an electrostatic field. In principle, you can measure the field at any point inspace by placing a small positive charge at that point and measuring the force exerted on it.You can use the definition of the field to determine the field created by variousdistributions of charge. The simplest and most important is the field created by a single pointcharge. Imagine a positive charge Q (figure 3). By symmetry, the magnitude of the field willdepend only on the distance from the charge, and the direction will be^radially outward. Ifyou bring a test charge to some point a distance R away, you have for E :Electric Force and Electric Field
Page 1: CHAPTEElectric Force and Electric F
Page 5 and 6: Physics B Review-4//C2//CFigure 5A
Page 7 and 8: PRACTICE EXERCISESSection I Multipl
Page 9 and 10: Physics B ReviewFigure 92. A noncon
Page 11 and 12: Physics B Review3 x IP"6 _ , 6 X IP

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