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
−−6 µC++6 µCr = 2 cm

Two point charges of −6 µC and +6 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +6 µCr = 2 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 3100 N/C

A proton (charge 1.602 × 10⁻¹⁹ C, mass 1.673 × 10⁻²⁷ kg) is in a uniform electric field of 3100 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 3100 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 1.673 × 10⁻²⁷ kg
a = m/s²
3.Medium
++5 µC++8 µC++5 µC4 cm + 6 cm

Three point charges lie on a straight line: +5 µC on the left, +5 µC on the right 10 cm away, and +8 µC between them, 4 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 = +5 µCqR = +5 µCqM = +8 µCrL = 4 cmrR = 6 cm
F = N
4.Medium
++2 µC++4 µCr = 10 cm

Two identical small metal spheres carry charges of +2 µC and +4 µC. They are touched together and then put back 10 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = +4 µCr = 10 cm
F = N
5.Hard
3 cm4 cm+q1​ = +3 µC+q3​ = +1 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 3 µC is 3 cm from it along one side and q₂ = 5 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 5 µCq3 = 1 µCr13 = 3 cmr23 = 4 cm
F = N
6.Hard
6 cm6 cm+q1​ = +10 µC+q3​ = +3 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 10 µC is 6 cm from it along one side and q₂ = 1 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 1 µCq3 = 3 µCr13 = 6 cmr23 = 6 cm
F = N

Answer key

  1. 1. F = 809.1 N
  2. 2. a = 2.968 × 10¹¹ m/s²
  3. 3. F = 124.9 N
  4. 4. F = 8.091 N
  5. 5. F = 41.08 N
  6. 6. F = 75.29 N

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