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 = 2200 N/C

A proton (charge 1.602 × 10⁻¹⁹ C, mass 1.673 × 10⁻²⁷ kg) is in a uniform electric field of 2200 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2200 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 1.673 × 10⁻²⁷ kg
a = m/s²
2.Easy
−−1 µCPr = 8 cm

Find the magnitude of the electric field E at a distance of 8 cm from a point charge of −1 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −1 µCr = 8 cm
E = N/C
3.Medium
++2 µC++8 µCP30 cm

A charge of +2 µC and a charge of +8 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 = +2 µCq2 = +8 µCr1 = 15 cmr2 = 15 cm
E = N/C
4.Medium
++10 µC−−6 µC−−3 µC5 cm + 5 cm

Three point charges lie on a straight line: +10 µC on the left, −3 µC on the right 10 cm away, and −6 µC between them, 5 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².

qL = +10 µCqR = −3 µCqM = −6 µCrL = 5 cmrR = 5 cm
F = N
5.Hard
10 cm8 cm+q1​ = +2 µC+q3​ = +6 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 2 µC is 10 cm from it along one side and q₂ = 1 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 1 µCq3 = 6 µCr13 = 10 cmr23 = 8 cm
F = N
6.Hard
++P2 × 4 cm8 cm+1 µC+1 µC

Charges of +1 µC and +1 µC are 8 cm apart. Point P lies 8 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 = +1 µCq2 = +1 µCd = 8 cmh = 8 cm
E = N/C

Answer key

  1. 1. a = 2.107 × 10¹¹ m/s²
  2. 2. E = 1.405 × 10⁶ N/C
  3. 3. E = 2.397 × 10⁶ N/C
  4. 4. F = 280.5 N
  5. 5. F = 13.69 N
  6. 6. E = 2.01 × 10⁶ N/C

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