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
++1 µC++6 µCr = 5 cm

Two point charges of +1 µC and +6 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = +6 µCr = 5 cm
F = N
2.Easy
++6 µC++1 µCr = 5 cm

Two point charges of +6 µC and +1 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +6 µCq2 = +1 µCr = 5 cm
F = N
3.Medium
++8 µC++10 µCE = 060 cm

Charges of +8 µC and +10 µC are 60 cm apart. At what distance x from the +8 µC charge, on the line between them, is the electric field zero?

q1 = +8 µCq2 = +10 µCd = 60 cm
x = cm
4.Medium
++8 µC−−1 µCP40 cm

A charge of +8 µC and a charge of −1 µC are 40 cm apart. Point P lies on the line between them, 16 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = −1 µCr1 = 16 cmr2 = 24 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻1 × 10⁷ m/s5 cmE = 4100 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1 × 10⁷ m/s. The plates are 5 cm long and the field between them is 4100 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 = 1 × 10⁷ m/sL = 5 cmE = 4100 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
5 cm3 cm+q1​ = +10 µC+q3​ = +4 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 10 µC is 5 cm from it along one side and q₂ = 3 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 3 µCq3 = 4 µCr13 = 5 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 21.58 N
  2. 2. F = 21.58 N
  3. 3. x = 28.33 cm
  4. 4. E = 2.965 × 10⁶ N/C
  5. 5. y = 9.013 mm
  6. 6. F = 187.2 N

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