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
++50 nCPr = 25 cm

Find the magnitude of the electric field E at a distance of 25 cm from a point charge of +50 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +50 nCr = 25 cm
E = N/C
2.Easy
+ + + + + +− − − − − −e⁻E = 3700 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 3700 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 3700 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
−−1 µC++10 µCr = 5 cm

Two identical small metal spheres carry charges of −1 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 = −1 µCq2 = +10 µCr = 5 cm
F = N
4.Medium
++1 µC++5 µCP30 cm

A charge of +1 µC and a charge of +5 µC are 30 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 = +5 µCr1 = 15 cmr2 = 15 cm
E = N/C
5.Hard
5 cm8 cm+q1​ = +10 µC+q3​ = +3 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 10 µC is 5 cm from it along one side and q₂ = 2 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 2 µCq3 = 3 µCr13 = 5 cmr23 = 8 cm
F = N
6.Hard
6 cm8 cm+q1​ = +10 µC+q3​ = +1 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 10 µC is 6 cm from it along one side and q₂ = 3 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 3 µCq3 = 1 µCr13 = 6 cmr23 = 8 cm
F = N

Answer key

  1. 1. E = 7192 N/C
  2. 2. a = 6.507 × 10¹⁴ m/s²
  3. 3. F = 72.82 N
  4. 4. E = 1.598 × 10⁶ N/C
  5. 5. F = 108.2 N
  6. 6. F = 25.33 N

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