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
++2 µCPr = 8 cm

Find the magnitude of the electric field E at a distance of 8 cm from a point charge of +2 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = +2 µCr = 8 cm
E = N/C
2.Easy
−−40 nCPr = 40 cm

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

q = −40 nCr = 40 cm
E = N/C
3.Medium
++5 µC++6 µCP10 cm

A charge of +5 µC and a charge of +6 µC are 10 cm apart. Point P lies on the line between them, 2.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +6 µCr1 = 2.5 cmr2 = 7.5 cm
E = N/C
4.Medium
++2 µC++5 µCP40 cm

A charge of +2 µC and a charge of +5 µC are 40 cm apart. Point P lies on the line between them, 10 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = +5 µCr1 = 10 cmr2 = 30 cm
E = N/C
5.Hard
4 cm4 cm+q1​ = +6 µC+q3​ = +2 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 6 µC is 4 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 = 2 µCr13 = 4 cmr23 = 4 cm
F = N
6.Hard
+ + + + + +− − − − − −e⁻2 × 10⁷ m/s8 cmE = 1900 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2 × 10⁷ m/s. The plates are 8 cm long and the field between them is 1900 N/C. Electron charge 1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg; ignore gravity. How far y is it deflected sideways when it leaves the plates? Give the answer in mm.

v₀ = 2 × 10⁷ m/sL = 8 cmE = 1900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. E = 2.809 × 10⁶ N/C
  2. 2. E = 2247 N/C
  3. 3. E = 6.233 × 10⁷ N/C
  4. 4. E = 1.299 × 10⁶ N/C
  5. 5. F = 68.36 N
  6. 6. y = 2.673 mm

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