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
−−40 nCPr = 20 cm

Find the magnitude of the electric field E at a distance of 20 cm from a point charge of −40 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = −40 nCr = 20 cm
E = N/C
2.Easy
−−6 µC++10 µCr = 8 cm

Two point charges of −6 µC and +10 µC are 8 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 = 8 cm
F = N
3.Medium
−−6 µC−−4 µCr = 40 cm

Two identical small metal spheres carry charges of −6 µC and −4 µC. They are touched together and then put back 40 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = −4 µCr = 40 cm
F = N
4.Medium
++1 µC++10 µCE = 0100 cm

Charges of +1 µC and +10 µC are 100 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 = 100 cm
x = cm
5.Hard
8 cm3 cm+q1​ = +4 µC+q3​ = +3 µC+q2​ = +8 µC

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

q1 = 4 µCq2 = 8 µCq3 = 3 µCr13 = 8 cmr23 = 3 cm
F = N
6.Hard
3 cm10 cm+q1​ = +10 µC+q3​ = +4 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 10 µC is 3 cm from it along one side and q₂ = 3 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 3 µCq3 = 4 µCr13 = 3 cmr23 = 10 cm
F = N

Answer key

  1. 1. E = 8990 N/C
  2. 2. F = 84.28 N
  3. 3. F = 1.405 N
  4. 4. x = 24.03 cm
  5. 5. F = 240.3 N
  6. 6. F = 399.7 N

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