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++10 µCr = 12 cm

Two point charges of −6 µC and +10 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +10 µCr = 12 cm
F = N
2.Easy
++2 µCPr = 30 cm

Find the magnitude of the electric field E at a distance of 30 cm from a point charge of +2 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = +2 µCr = 30 cm
E = N/C
3.Medium
−−4 µC++10 µCr = 5 cm

Two identical small metal spheres carry charges of −4 µC and +10 µC. They are touched together and then put back 5 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −4 µCq2 = +10 µCr = 5 cm
F = N
4.Medium
++5 µC++3 µCP60 cm

A charge of +5 µC and a charge of +3 µC are 60 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 = +5 µCq2 = +3 µCr1 = 30 cmr2 = 30 cm
E = N/C
5.Hard
10 cm10 cm+q1​ = +5 µC+q3​ = +10 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 10 µC is at the right-angle corner, q₁ = 5 µC is 10 cm from it along one side and q₂ = 4 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 5 µCq2 = 4 µCq3 = 10 µCr13 = 10 cmr23 = 10 cm
F = N
6.Hard
6 cm3 cm+q1​ = +10 µC+q3​ = +5 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 5 µC is at the right-angle corner, q₁ = 10 µC is 6 cm from it along one side and q₂ = 10 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 10 µCq3 = 5 µCr13 = 6 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 37.46 N
  2. 2. E = 199778 N/C
  3. 3. F = 32.36 N
  4. 4. E = 199778 N/C
  5. 5. F = 57.56 N
  6. 6. F = 514.8 N

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