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
++3 µC−−2 µCr = 6 cm

Two point charges of +3 µC and −2 µC are 6 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +3 µCq2 = −2 µCr = 6 cm
F = N
2.Easy
−−5 µCPr = 25 cm

Find the magnitude of the electric field E at a distance of 25 cm from a point charge of −5 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −5 µCr = 25 cm
E = N/C
3.Medium
++10 µC++4 µCP50 cm

A charge of +10 µC and a charge of +4 µC are 50 cm apart. Point P lies on the line between them, 30 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +10 µCq2 = +4 µCr1 = 30 cmr2 = 20 cm
E = N/C
4.Medium
++10 µC++2 µCP20 cm

A charge of +10 µC and a charge of +2 µC are 20 cm apart. Point P lies on the line between them, 5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +10 µCq2 = +2 µCr1 = 5 cmr2 = 15 cm
E = N/C
5.Hard
5 cm10 cm+q1​ = +8 µC+q3​ = +3 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 8 µC is 5 cm from it along one side and q₂ = 10 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 10 µCq3 = 3 µCr13 = 5 cmr23 = 10 cm
F = N
6.Hard
+−P2 × 10 cm5 cm+3 µC−3 µC

Charges of +3 µC and −3 µC are 20 cm apart. Point P lies 5 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 = +3 µCq2 = −3 µCd = 20 cmh = 5 cm
E = N/C

Answer key

  1. 1. F = 14.98 N
  2. 2. E = 719200 N/C
  3. 3. E = 99889 N/C
  4. 4. E = 3.516 × 10⁷ N/C
  5. 5. F = 90.42 N
  6. 6. E = 3.86 × 10⁶ N/C

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