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
++5 µC−−2 µCr = 25 cm

Two point charges of +5 µC and −2 µC are 25 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 = 25 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 2500 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2500 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2500 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
−−3 µC++5 µCr = 30 cm

Two identical small metal spheres carry charges of −3 µC and +5 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 = −3 µCq2 = +5 µCr = 30 cm
F = N
4.Medium
++2 µC++1 µCr = 40 cm

Two identical small metal spheres carry charges of +2 µC and +1 µC. They are touched together and then put back 40 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = +1 µCr = 40 cm
F = N
5.Hard
6 cm6 cm+q1​ = +5 µC+q3​ = +5 µC+q2​ = +8 µC

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

q1 = 5 µCq2 = 8 µCq3 = 5 µCr13 = 6 cmr23 = 6 cm
F = N
6.Hard
++P2 × 3 cm6 cm+2 µC+2 µC

Charges of +2 µC and +2 µC are 6 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 = +2 µCq2 = +2 µCd = 6 cmh = 6 cm
E = N/C

Answer key

  1. 1. F = 1.438 N
  2. 2. a = 4.397 × 10¹⁴ m/s²
  3. 3. F = 0.09989 N
  4. 4. F = 0.1264 N
  5. 5. F = 117.8 N
  6. 6. E = 7.147 × 10⁶ N/C

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