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
++10 nCPr = 15 cm

Find the magnitude of the electric field E at a distance of 15 cm from a point charge of +10 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +10 nCr = 15 cm
E = N/C
2.Easy
++10 nCPr = 10 cm

Find the magnitude of the electric field E at a distance of 10 cm from a point charge of +10 nC. Use k = 8.99 × 10⁹ N·m²/C².

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

A charge of +4 µC and a charge of −3 µC are 50 cm apart. Point P lies on the line between them, 37.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +4 µCq2 = −3 µCr1 = 37.5 cmr2 = 12.5 cm
E = N/C
4.Medium
++1 µC−−3 µCP60 cm

A charge of +1 µC and a charge of −3 µC are 60 cm apart. Point P lies on the line between them, 15 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −3 µCr1 = 15 cmr2 = 45 cm
E = N/C
5.Hard
4 cm6 cm+q1​ = +2 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 = 2 µC is 4 cm from it along one side and q₂ = 5 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 5 µCq3 = 1 µCr13 = 4 cmr23 = 6 cm
F = N
6.Hard
8 cm8 cm+q1​ = +3 µC+q3​ = +8 µC+q2​ = +1 µC

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

q1 = 3 µCq2 = 1 µCq3 = 8 µCr13 = 8 cmr23 = 8 cm
F = N

Answer key

  1. 1. E = 3996 N/C
  2. 2. E = 8990 N/C
  3. 3. E = 1.982 × 10⁶ N/C
  4. 4. E = 532741 N/C
  5. 5. F = 16.8 N
  6. 6. F = 35.54 N

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