Consider three 1-nC magnitude charges B, C, and D configured as shown in Fig. 1.
ID: 1316125 • Letter: C
Question
Consider three 1-nC magnitude charges B, C, and D configured as shown in Fig. 1. Each small square in the
grid has sides of 0.2 m.
7. What is the magnitude of the electric field in N/C at point A due to the charge configuration in Fig. 1?
8. What is the direction of the electric field at point A due to the charge configuration in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
9. What is the magnitude of the electric force in nN exerted on a +1 nC charge placed at point A in Fig. 1?
10. What is the direction of the electric force exerted on a +1 nC charge placed at point A in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
11. What is the magnitude of the electric force in nN exerted on a ?2 nC charge placed at point A in Fig. 1?
12. What is the direction of the electric force exerted on a ?2 nC test charge placed at point A in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
13. What is the electric potential in J/C at point A due to charge B in Fig. 1?
14. What is the direction of the electric potential at point A due to charge B in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
15. What is the electric potential in J/C at point A due to charge C in Fig. 1?
16. What is the direction of the electric potential at point A due to charge C in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
17. What is the electric potential in J/C at point A due to charge D in Fig. 1?
18. What is the direction of the electric potential at point A due to charge D in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
19. What is the electric potential in J/C at point A due to the charge configuration in Fig. 1?
20. What is the direction of the electric potential at point A due to the charge configuration in Fig. 1? (options: to the right, to the left, up, down, some other angle, Trick question! The electric field doesn't have a direction)
Explanation / Answer
B = C = -1 * 10-9 C at a distance r = 1 m from point A
D = 1 * 10-9 C at a distance r = 2 m from A
k = 8.99 * 109 N.m2 / C2 is the Coulomb's force constant.
7. What is the magnitude of the electric field in N/C at point A due to the charge configuration in Fig. 1?
X component of the electric field at A due to the charge configuration in Fig. 1 is,
Ex = k B cos 180 / 12 + k C cos 0 / 12 + k D cos 270 / 22
Ex = 8.99 * 109 * 10-9 * [-1 + 1 + 0]
Ex = 0 N/C
Y component of the electric field at A due to the charge configuration in Fig. 1 is,
Ey = k B sin 180 / 12 + k C sin 0 / 12 + k D sin 270 / 22
Ey = 8.99 * 109 * 10-9 * [0 + 0 - 1/4]
Ey = - 2.2475 N/C
Thus, the magnitude of the electric field in N/C at point A due to the charge configuration in Fig. 1 is,
E = (Ex2 + Ey2)1/2
E = 5.05 N/C
8. What is the direction of the electric field at point A due to the charge configuration in Fig. 1?
The direction is downward. Electric field is a vector quantity and has direction.
9. What is the magnitude of the electric force in nN exerted on a +1 nC charge placed at point A in Fig. 1?
Magnitude of force on charge q = 1 * 10-9 C is,
F = q E
F = 1 * 10-9 * 5.05
F = 5.05 * 10-9 N
10. What is the direction of the electric force exerted on a +1 nC charge placed at point A in Fig. 1?
The direction is downward.
11. What is the magnitude of the electric force in nN exerted on a ?2 nC charge placed at point A in Fig. 1?
Magnitude of force on charge q = -2 * 10-9 C is,
F = q E
F = -2 * 10-9 * 5.05
F = - 10.1 * 10-9 N = -1.01 * 10-8 N
12. What is the direction of the electric force exerted on a ?2 nC test charge placed at point A in Fig. 1?
The direction is upward.
13. What is the electric potential in J/C at point A due to charge B in Fig. 1?
V = k q /r
V = - 8.99 * 109 * 1 * 10-9 / 1
V = - 8.99 J/C
14. What is the direction of the electric potential at point A due to charge B in Fig. 1?
Electric potential is a scalar quantity and hence doesn't have direction.
15. What is the electric potential in J/C at point A due to charge C in Fig. 1?
V = k q /r
V = - 8.99 * 109 * 1 * 10-9 / 1
V = - 8.99 J/C
16. What is the direction of the electric potential at point A due to charge C in Fig. 1?
Electric potential is a scalar quantity and hence doesn't have direction.
17. What is the electric potential in J/C at point A due to charge D in Fig. 1?
V = k q /r
V = 8.99 * 109 * 1 * 10-9 / 2
V = 4.495 J/C
18. What is the direction of the electric potential at point A due to charge D in Fig. 1?
Electric potential is a scalar quantity and hence doesn't have direction.
19. What is the electric potential in J/C at point A due to the charge configuration in Fig. 1?
V = k B / 1 + k C / 1 + k D / 2
V = 8.99 * 109 * 10-9 * [- 1 - 1 + (1/2)]
V = -13.385 J/C
20. What is the direction of the electric potential at point A due to the charge configuration in Fig. 1?
Electric potential is a scalar quantity and hence doesn't have direction.