PHYS 2212 Module 1.4

Electric Field

Recommended Reading

1.4 Electric Field

Learning Objectives

By the end of this section, you will be able to:

  • Explain the purpose of the electric field concept
  • Describe the properties of the electric field
  • Calculate the field of a collection of source charges of either sign

Electric Field

Discuss!

Reflect on this question and take notes on how you would answer it. Then we will share these thoughts together in a class discussion.

What is the magnitude of an electric field in which the electric force on a proton is equal in magnitude to its weight?

What must the charge (sign and magnitude) of a particle of mass 1.46 g be for it to remain stationary when placed in a downward-directed electric field of magnitude 660 N/C?

Pause & Predict 1.4.1
At what distance from a +1.9 nC point charge will the electric field have a magnitude of 2.2 × 105 N/C?
Pause & Predict 1.4.2
What is the electric field produced at point P by a dipole of ±q = 3.2 nC and a dipole separation of d = 750 mm?
A. 72 N/C
B. 144 N/C
C. 102 N/C
D. 46 N/C
E. 330 N/C

Practice!

Practice 1.4.1
A point charge of +7.45 pC (7.45 ´ 10-12 C) is fixed at the origin. What is the electric field produced by this charge at point P, which is on the x-axis, 9.83 mm from the origin?
A. 6.81 N/C
B. 6.81 N/C (-)
C. 693 N/C
D. 693 N/C (-)
E. 5.16 nN/C
F. 5.16 nN/C (-)
Check your answer here: C. 693 N/C
Practice 1.4.2
A point charge of -4.28 pC is fixed on the y-axis, 2.79 mm from the origin. What is the electric field produced by this charge at point P, which is on the x-axis, 9.83 mm from the origin?
A. 101 N/C (-) + 355 N/C
B. 355 N/C (-) + 101 N/C
C. 369 N/C
D. 4940 N/C
E. 398 N/C (- )
Practice 1.4.3
A point charge of +7.45 pC (7.45 x 10-12 C) is fixed at the origin. Another point charge of -4.28 pC is fixed on the y-axis, 2.79 mm from the origin. If you placed a proton at point P, which is on the x-axis, 9.83 mm from the origin, what would be the magnitude of the electric force on that proton?
A. 1050 N
B. 1.69 × 10-16 N
C, 353 N
D. 5.66 × 10-17 N