Coulomb’s law & electric fields worksheet with answers

Free printable Coulomb’s law & electric fields worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
−−1 µC−−1 µCr = 8 cm

Two point charges of −1 µC and −1 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = −1 µCr = 8 cm
F = N
2.Easy
−−8 µC++10 µCr = 3 cm

Two point charges of −8 µC and +10 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = +10 µCr = 3 cm
F = N
3.Medium
−−4 µC−−1 µCr = 20 cm

Two identical small metal spheres carry charges of −4 µC and −1 µC. They are touched together and then put back 20 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −4 µCq2 = −1 µCr = 20 cm
F = N
4.Medium
++6 µC++6 µCP20 cm

A charge of +6 µC and a charge of +6 µC are 20 cm apart. Point P lies on the line between them, 5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +6 µCq2 = +6 µCr1 = 5 cmr2 = 15 cm
E = N/C
5.Hard
++P2 × 10 cm5 cm+3 µC+3 µC

Charges of +3 µC and +3 µC are 20 cm apart. Point P lies 5 cm from the midpoint between them, on the perpendicular bisector. Find the magnitude of the electric field E at P. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +3 µCq2 = +3 µCd = 20 cmh = 5 cm
E = N/C
6.Hard
L = 60 cm8°qq

Two identical small balls, each of mass 2 g, hang from the same point on insulating threads 60 cm long. They are given equal charges and each thread settles at 8° from the vertical. Use g = 9.81 m/s². Find the charge q on each ball in nC. Use k = 8.99 × 10⁹ N·m²/C².

m = 2 gL = 60 cmθ = 8°g = 9.81 m/s²
q = nC

Answer key

  1. 1. F = 1.405 N
  2. 2. F = 799.1 N
  3. 3. F = 1.405 N
  4. 4. E = 1.918 × 10⁷ N/C
  5. 5. E = 1.93 × 10⁶ N/C
  6. 6. q = 92.49 nC

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