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
+ + + + + +− − − − − −e⁻E = 4500 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 4500 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 4500 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
2.Easy
−−8 µC−−8 µCr = 2 cm

Two point charges of −8 µC and −8 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = −8 µCr = 2 cm
F = N
3.Medium
−−8 µC−−10 µCr = 30 cm

Two identical small metal spheres carry charges of −8 µC and −10 µC. They are touched together and then put back 30 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = −10 µCr = 30 cm
F = N
4.Medium
++2 µC++5 µCP10 cm

A charge of +2 µC and a charge of +5 µC are 10 cm apart. Point P lies on the line between them, 6 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = +5 µCr1 = 6 cmr2 = 4 cm
E = N/C
5.Hard
10 cm4 cm+q1​ = +6 µC+q3​ = +10 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 10 µC is at the right-angle corner, q₁ = 6 µC is 10 cm from it along one side and q₂ = 1 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 1 µCq3 = 10 µCr13 = 10 cmr23 = 4 cm
F = N
6.Hard
8 cm10 cm+q1​ = +10 µC+q3​ = +10 µC+q2​ = +8 µC

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

q1 = 10 µCq2 = 8 µCq3 = 10 µCr13 = 8 cmr23 = 10 cm
F = N

Answer key

  1. 1. a = 7.914 × 10¹⁴ m/s²
  2. 2. F = 1438 N
  3. 3. F = 8.091 N
  4. 4. E = 2.31 × 10⁷ N/C
  5. 5. F = 77.89 N
  6. 6. F = 157.8 N

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