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−−5 µCr = 3 cm

Two point charges of −1 µC and −5 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = −5 µCr = 3 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 2900 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2900 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2900 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
++4 µC−−2 µCr = 30 cm

Two identical small metal spheres carry charges of +4 µC and −2 µC. They are touched together and then put back 30 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = −2 µCr = 30 cm
F = N
4.Medium
++5 µC++1 µCP40 cm

A charge of +5 µC and a charge of +1 µC are 40 cm apart. Point P lies on the line between them, 24 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +1 µCr1 = 24 cmr2 = 16 cm
E = N/C
5.Hard
++P2 × 6 cm6 cm+8 µC+8 µC

Charges of +8 µC and +8 µC are 12 cm apart. Point P lies 6 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 = +8 µCq2 = +8 µCd = 12 cmh = 6 cm
E = N/C
6.Hard
5 cm3 cm+q1​ = +6 µC+q3​ = +6 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 6 µC is 5 cm from it along one side and q₂ = 1 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 1 µCq3 = 6 µCr13 = 5 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 49.94 N
  2. 2. a = 5.1 × 10¹⁴ m/s²
  3. 3. F = 0.09989 N
  4. 4. E = 429210 N/C
  5. 5. E = 1.413 × 10⁷ N/C
  6. 6. F = 142.7 N

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