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

Two point charges of +6 µC and +4 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q₁ = +6 µCq₂ = +4 µCr = 5 cm

F = N

2.Easy

Two point charges of +6 µC and +3 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q₁ = +6 µCq₂ = +3 µCr = 8 cm

F = N

3.Medium

Charges of +2 µC and +8 µC are 30 cm apart. At what distance x from the +2 µC charge, on the line between them, is the electric field zero?

q₁ = +2 µCq₂ = +8 µCd = 30 cm

x = cm

4.Medium

Two identical small metal spheres carry charges of −4 µC and −5 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 = −5 µCr = 20 cm

F = N

5.Hard

Charges of +3 µC and +3 µC are 12 cm apart. Point P lies 10 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 = 12 cmh = 10 cm

E = N/C

6.Hard

Two identical small balls, each of mass 10 g, hang from the same point on insulating threads 50 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 = 10 gL = 50 cmθ = 15°g = 9.81 m/s²

q = nC

Answer key

1. F = 86.3 N
2. F = 25.28 N
3. x = 10 cm
4. F = 4.551 N
5. E = 3.401 × 10⁶ N/C
6. q = 442.6 nC

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