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
++4 µC++3 µCr = 2 cm

Two point charges of +4 µC and +3 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = +3 µCr = 2 cm
F = N
2.Easy
++1 µC++8 µCr = 15 cm

Two point charges of +1 µC and +8 µC are 15 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = +8 µCr = 15 cm
F = N
3.Medium
++8 µC−−6 µCP20 cm

A charge of +8 µC and a charge of −6 µC are 20 cm apart. Point P lies on the line between them, 15 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = −6 µCr1 = 15 cmr2 = 5 cm
E = N/C
4.Medium
++10 µC−−6 µCP10 cm

A charge of +10 µC and a charge of −6 µC are 10 cm apart. Point P lies on the line between them, 6 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +10 µCq2 = −6 µCr1 = 6 cmr2 = 4 cm
E = N/C
5.Hard
++P2 × 5 cm3 cm+1 µC+1 µC

Charges of +1 µC and +1 µC are 10 cm apart. Point P lies 3 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 = +1 µCq2 = +1 µCd = 10 cmh = 3 cm
E = N/C
6.Hard
L = 60 cm8°qq

Two identical small balls, each of mass 1 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 = 1 gL = 60 cmθ = 8°g = 9.81 m/s²
q = nC

Answer key

  1. 1. F = 269.7 N
  2. 2. F = 3.196 N
  3. 3. E = 2.477 × 10⁷ N/C
  4. 4. E = 5.868 × 10⁷ N/C
  5. 5. E = 2.721 × 10⁶ N/C
  6. 6. q = 65.4 nC

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