Question

9 Pi Three point charges, q1--e, q2-+2e, and q3 -e are arranged at(xiy)( 1,0), (xy2)-(0,0) andx y) (1,0) as shown on the above figure. Point P is located at (3,0). point Pz is at (0,1) and point Ps is at (0.5, 0), where all distances are given in metres and e 1602 x 10-1"C. 1. (a) Draw vectors labeled Е.. . E. and Eqs at point Pr to indicate the relative sizes and directions of the contributions to the electric field at this point due to each source charge. /4 (b) What direction is the net electric field due to these three charges at point P:? /1 (c) Find the electric field at point P y3 2. (a) Draw vectors labelled E.Ez and E at point P to indicate the relative sizes and directions of the contributions to the electric field at this point due to each source charge. /4 (b) What direction is the net electric field due to these three charges at point P:? 2 (c) Find the electric field at point P2. /4 3. (a) Draw vectors labelled Ei,Eg2 and E3 at point P to indicate the relative sizes and directions of the contributions to the electric field at this point due to each source charge. /4 (b) What direction is the net electric field due to these three charges at point Ps? /1 (c) Find the electric field at point Ps. /4

Answer 1

(a) (b) obviously, from diagram 1, the net field is along E p_3 (or -ve x - axis) (c) At p_1 E_p, net = E p_1 + E p_3 - E p_2 = k q/(4)^2 + k q/(2)^2 - 2 k q/(3)^2 [where q = e] = k q [1/16 + 1/4 - 2/5] = 9 times 10^9 times 1.602 times 10^- 19 [9 + 36 - 32/144] E p_1, net = 1.30 times 10^- 10 N/C answer