Question

31. Three point charges are located on a circular arc as shown in Figure P23.31. (a) What is the total electric field at P, the center of the arc? (b) Find the elec- tric force that would be exerted on a -5.00-nC point charge placed at F +3.00 nC 4.00 cm -2.00 nC 30.0 30.0。 4.00 cm +3.00 nC Figure P23.31

Answer 1

electric field due to 3 nC ( upper)

E = k q / r^2 = 9*10^9 * 3*10^-9 / 0.04^2 ( cos 30 i + sin 30 j)

E1 = 16875* (cos 30 i + sin 30 j)

similarly electric field due to 3 nC (lower)

E2 = 16875 * ( cos 30 i - sin 30 j)

electric field due to - 2 nC

E3 = 9*10^9* 2*10^-9 / 0.04^2 = - 11250 i

net electric field

E = E1 + E2 + E3

E = 16875 * 2* cos 30 - 11250

E = 17978.36 N/C

directed along +x axis

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force acting on given charge

F = qE = 17978.36* 5*10^-9 = 8.99*10^-5 N

directed along - x axis

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