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 −5 µC and +2 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q₁ = −5 µCq₂ = +2 µCr = 12 cm

F = N

2.Easy

Two point charges of +4 µC and −8 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q₁ = +4 µCq₂ = −8 µCr = 12 cm

F = N

3.Medium

Charges of +4 µC and +1 µC are 100 cm apart. At what distance x from the +4 µC charge, on the line between them, is the electric field zero?

q₁ = +4 µCq₂ = +1 µCd = 100 cm

x = cm

4.Medium

Charges of +4 µC and +2 µC are 80 cm apart. At what distance x from the +4 µC charge, on the line between them, is the electric field zero?

q₁ = +4 µCq₂ = +2 µCd = 80 cm

x = cm

5.Hard

Two identical small balls, each of mass 5 g, hang from the same point on insulating threads 30 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 = 5 gL = 30 cmθ = 10°g = 9.81 m/s²

q = nC

6.Hard

Two identical small balls, each of mass 5 g, hang from the same point on insulating threads 60 cm long. They are given equal charges and each thread settles at 20° 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 = 5 gL = 60 cmθ = 20°g = 9.81 m/s²

q = nC

Answer key

1. F = 6.243 N
2. F = 19.98 N
3. x = 66.67 cm
4. x = 46.86 cm
5. q = 102.2 nC
6. q = 578.4 nC

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