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 = 8 cm

Two point charges of −1 µC and −6 µC are 8 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 = 8 cm
F = N
2.Easy
−−6 µC−−10 µCr = 10 cm

Two point charges of −6 µC and −10 µC are 10 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = −10 µCr = 10 cm
F = N
3.Medium
++10 µC++5 µCE = 040 cm

Charges of +10 µC and +5 µC are 40 cm apart. At what distance x from the +10 µC charge, on the line between them, is the electric field zero?

q1 = +10 µCq2 = +5 µCd = 40 cm
x = cm
4.Medium
++5 µC++1 µCP30 cm

A charge of +5 µC and a charge of +1 µC are 30 cm apart. Point P lies on the line between them, 22.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +1 µCr1 = 22.5 cmr2 = 7.5 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻2.5 × 10⁷ m/s8 cmE = 3700 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2.5 × 10⁷ m/s. The plates are 8 cm long and the field between them is 3700 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 = 2.5 × 10⁷ m/sL = 8 cmE = 3700 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
8 cm3 cm+q1​ = +10 µC+q3​ = +4 µC+q2​ = +1 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 8 cm from it along one side and q₂ = 1 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 1 µCq3 = 4 µCr13 = 8 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 8.428 N
  2. 2. F = 53.94 N
  3. 3. x = 23.43 cm
  4. 4. E = 710321 N/C
  5. 5. y = 3.332 mm
  6. 6. F = 68.95 N

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