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
+ + + + + +− − − − − −e⁻E = 800 N/C

A proton (charge 1.602 × 10⁻¹⁹ C, mass 1.673 × 10⁻²⁷ kg) is in a uniform electric field of 800 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 800 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 1.673 × 10⁻²⁷ kg
a = m/s²
2.Easy
−−3 µCPr = 5 cm

Find the magnitude of the electric field E at a distance of 5 cm from a point charge of −3 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −3 µCr = 5 cm
E = N/C
3.Medium
++5 µC−−10 µCP40 cm

A charge of +5 µC and a charge of −10 µC are 40 cm apart. Point P lies on the line between them, 16 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = −10 µCr1 = 16 cmr2 = 24 cm
E = N/C
4.Medium
−−3 µC++6 µC−−10 µC12 cm + 8 cm

Three point charges lie on a straight line: −3 µC on the left, −10 µC on the right 20 cm away, and +6 µC between them, 12 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 = −3 µCqR = −10 µCqM = +6 µCrL = 12 cmrR = 8 cm
F = N
5.Hard
8 cm6 cm+q1​ = +1 µC+q3​ = +3 µC+q2​ = +3 µC

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

q1 = 1 µCq2 = 3 µCq3 = 3 µCr13 = 8 cmr23 = 6 cm
F = N
6.Hard
3 cm4 cm+q1​ = +8 µC+q3​ = +2 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 8 µC is 3 cm from it along one side and q₂ = 4 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 4 µCq3 = 2 µCr13 = 3 cmr23 = 4 cm
F = N

Answer key

  1. 1. a = 7.66 × 10¹⁰ m/s²
  2. 2. E = 1.079 × 10⁷ N/C
  3. 3. E = 3.317 × 10⁶ N/C
  4. 4. F = 73.04 N
  5. 5. F = 22.87 N
  6. 6. F = 166 N

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