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 nCPr = 2 cm

Find the magnitude of the electric field E at a distance of 2 cm from a point charge of −5 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = −5 nCr = 2 cm
E = N/C
2.Easy
−−2 µC++5 µCr = 2 cm

Two point charges of −2 µC and +5 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −2 µCq2 = +5 µCr = 2 cm
F = N
3.Medium
−−8 µC−−1 µC−−2 µC12 cm + 8 cm

Three point charges lie on a straight line: −8 µC on the left, −2 µC on the right 20 cm away, and −1 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 = −8 µCqR = −2 µCqM = −1 µCrL = 12 cmrR = 8 cm
F = N
4.Medium
++1 µC++10 µCE = 060 cm

Charges of +1 µC and +10 µC are 60 cm apart. At what distance x from the +1 µC charge, on the line between them, is the electric field zero?

q1 = +1 µCq2 = +10 µCd = 60 cm
x = cm
5.Hard
10 cm6 cm+q1​ = +2 µC+q3​ = +8 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 2 µC is 10 cm from it along one side and q₂ = 10 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 10 µCq3 = 8 µCr13 = 10 cmr23 = 6 cm
F = N
6.Hard
+−P2 × 6 cm4 cm+2 µC−2 µC

Charges of +2 µC and −2 µC are 12 cm apart. Point P lies 4 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 = 12 cmh = 4 cm
E = N/C

Answer key

  1. 1. E = 112375 N/C
  2. 2. F = 224.7 N
  3. 3. F = 2.185 N
  4. 4. x = 14.42 cm
  5. 5. F = 200.3 N
  6. 6. E = 5.754 × 10⁶ N/C

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