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
−−200 nCPr = 3 cm

Find the magnitude of the electric field E at a distance of 3 cm from a point charge of −200 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = −200 nCr = 3 cm
E = N/C
2.Easy
+ + + + + +− − − − − −e⁻E = 2100 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2100 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2100 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
−−2 µC++6 µCr = 50 cm

Two identical small metal spheres carry charges of −2 µC and +6 µC. They are touched together and then put back 50 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −2 µCq2 = +6 µCr = 50 cm
F = N
4.Medium
++10 µC−−4 µC++4 µC30 cm + 10 cm

Three point charges lie on a straight line: +10 µC on the left, +4 µC on the right 40 cm away, and −4 µC between them, 30 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².

qL = +10 µCqR = +4 µCqM = −4 µCrL = 30 cmrR = 10 cm
F = N
5.Hard
8 cm5 cm+q1​ = +1 µC+q3​ = +6 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 1 µC is 8 cm from it along one side and q₂ = 3 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 3 µCq3 = 6 µCr13 = 8 cmr23 = 5 cm
F = N
6.Hard
4 cm10 cm+q1​ = +4 µC+q3​ = +2 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 4 µC is 4 cm from it along one side and q₂ = 6 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 6 µCq3 = 2 µCr13 = 4 cmr23 = 10 cm
F = N

Answer key

  1. 1. E = 1.998 × 10⁶ N/C
  2. 2. a = 3.693 × 10¹⁴ m/s²
  3. 3. F = 0.1438 N
  4. 4. F = 10.39 N
  5. 5. F = 65.27 N
  6. 6. F = 46.23 N

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