Question
number 4 please
e) If the right end of the uniformly-charged rod were extended to an infinite distance
along the positive x-axis, determine the magnitude and direction of the net electric
field at point P(0,3) m.
[(a) ( -1.5, 0) kN/C; (b) (3, -6) kN/C; (c) 35.3 kN/C; (d) (7, -9) N/C; (e) (10.6 kN/C, 225o
)]
297:21 1:31 PM P221 2sp2018-practice-test-01-electricfields (1).pdf PHYS-2212 Practice Test SP-2018 Due: Name: ELECTRIC FORCES& FIELDS Two particles with charges, q,-3 x 10-6 C and q2 = 12 x 10" C, are located along the x-axis at positions with coordinates (0, 0) and (4, 0) m respectively. All distances are in meters. At what point along the x-axis should a third charge g 5 x 106 C be placed such that the net electric force on it is zero? 1.33,0) m 1. 2· Three point charges are placed at the vertices of a rectangle as shown. (a) Determine th 10nC 4 cm e magnitude and direction of the net electric field at the vacant vertex, as shown. (b) What electric force will be exerted on a fourth Sem charge, q15 nC, placed at the same vacant vertex? [(a) 145 kN/C, 730 (b) 2.2 mN, 253] 15 nC 3. A charged styrofoam ball of mass 2 g is suspended from a point on the ceiling by a thread and placed inside an electric field, E. The electric field vector is given as, E (5i + 4j)x 105N/C. Inside the electric field, the thread hangs at an angle of 30 from the vertical, as shown. (a) Determine the charge q on the ball. State whether this 30 charge is positive or negative and why (b) What is the magnitude of the tension in the thread? ((a) 1.55 x 10 C, (b) 1.55 x 10 N 2.0g 4. A plastic rod of finite length carries a uniformn linear charge Q-"10 C along the x- axis, with the left edge of the rod at the origin (O, 0) and its right edge at (4, 0) m. All distances are measured in meters, (a) Determine the net electric field at a point (10,0) m, along the positive x-axis. (b) Apply integral methods to find the x- and y components of the electric field vector due to this charged rod at the point P(0. 3) m, along the y-axis. the magnitude of the electric field at the center of this semicircle. if the rod carried a non-uniform charge density, = Cr, where the constant (c) When this uniformly-charged charged plastic rod is bent into a semicircle, find (d) What would be the rectangular components of the electric field at the point P(O, 3) C -2.5 nCh? (e) If the right end of the uniformly-charged rod were extended to an infinite distance along the positive x-axis, determine the magnitude and direction of the net electric field at point P0,3) m (a) -1.5, 0) kN/C; (b) (3,-6) kNC; (c) 35.3 kNC; (d) (-9) NC; (e) (10.6 kNC. 225") PHYS-2212 Practice Test SP-2018 Due: Name: ELECTRIC FORCES &FIELDS;
Explanation / Answer
Using coulombs law
The net force acting at a third point must be zero
Therefore equivalent force acting at third point due to other 2 charges must be zero
The force acting due to first charge F1=K*3*10^-6*q1/x^2
The force acting due to second charge F2=K*12*10^-6*q2/(4-x) ^2
F1=F2
Solving this we get x=1.33m
