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−−5 µCr = 8 cm

Two point charges of +6 µC and −5 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 = −5 µCr = 8 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 1000 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 1000 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 1000 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
++4 µC−−6 µCP30 cm

A charge of +4 µC and a charge of −6 µC are 30 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +4 µCq2 = −6 µCr1 = 7.5 cmr2 = 22.5 cm
E = N/C
4.Medium
++8 µC++2 µCP40 cm

A charge of +8 µC and a charge of +2 µC are 40 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 = +8 µCq2 = +2 µCr1 = 30 cmr2 = 10 cm
E = N/C
5.Hard
3 cm4 cm+q1​ = +6 µC+q3​ = +4 µC+q2​ = +8 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 6 µC is 3 cm from it along one side and q₂ = 8 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 8 µCq3 = 4 µCr13 = 3 cmr23 = 4 cm
F = N
6.Hard
++P2 × 8 cm5 cm+8 µC+8 µC

Charges of +8 µC and +8 µC are 16 cm apart. Point P lies 5 cm from the midpoint between them, on the perpendicular bisector. Find the magnitude of the electric field E at P. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +8 µCq2 = +8 µCd = 16 cmh = 5 cm
E = N/C

Answer key

  1. 1. F = 42.14 N
  2. 2. a = 1.759 × 10¹⁴ m/s²
  3. 3. E = 7.458 × 10⁶ N/C
  4. 4. E = 998889 N/C
  5. 5. F = 299.7 N
  6. 6. E = 8.566 × 10⁶ N/C

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