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
−−6 µCPr = 20 cm

Find the magnitude of the electric field E at a distance of 20 cm from a point charge of −6 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −6 µCr = 20 cm
E = N/C
2.Easy
−−6 µC++10 µCr = 25 cm

Two point charges of −6 µC and +10 µC are 25 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +10 µCr = 25 cm
F = N
3.Medium
++10 µC−−10 µCP10 cm

A charge of +10 µC and a charge of −10 µC are 10 cm apart. Point P lies on the line between them, 2.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +10 µCq2 = −10 µCr1 = 2.5 cmr2 = 7.5 cm
E = N/C
4.Medium
++2 µC−−2 µCP10 cm

A charge of +2 µC and a charge of −2 µC are 10 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = −2 µCr1 = 7.5 cmr2 = 2.5 cm
E = N/C
5.Hard
L = 50 cm10°qq

Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 50 cm long. They are given equal charges and each thread settles at 10° 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 = 1 gL = 50 cmθ = 10°g = 9.81 m/s²
q = nC
6.Hard
L = 100 cm15°qq

Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 100 cm long. They are given equal charges and each thread settles at 15° 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 = 1 gL = 100 cmθ = 15°g = 9.81 m/s²
q = nC

Answer key

  1. 1. E = 1.348 × 10⁶ N/C
  2. 2. F = 8.63 N
  3. 3. E = 1.598 × 10⁸ N/C
  4. 4. E = 3.196 × 10⁷ N/C
  5. 5. q = 76.17 nC
  6. 6. q = 279.9 nC

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