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
++4 µC−−10 µCr = 12 cm

Two point charges of +4 µC and −10 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = −10 µCr = 12 cm
F = N
2.Easy
++1 µC−−8 µCr = ?

Point charges of +1 µC and −8 µC exert a force of 2 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = −8 µCF = 2 N
r = cm
3.Medium
++4 µC++1 µC−−6 µC10 cm + 30 cm

Three point charges lie on a straight line: +4 µC on the left, −6 µC on the right 40 cm away, and +1 µC between them, 10 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 = +4 µCqR = −6 µCqM = +1 µCrL = 10 cmrR = 30 cm
F = N
4.Medium
++5 µC−−2 µCP30 cm

A charge of +5 µC and a charge of −2 µC are 30 cm apart. Point P lies on the line between them, 18 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = −2 µCr1 = 18 cmr2 = 12 cm
E = N/C
5.Hard
5 cm8 cm+q1​ = +1 µC+q3​ = +3 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 1 µC is 5 cm from it along one side and q₂ = 6 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 6 µCq3 = 3 µCr13 = 5 cmr23 = 8 cm
F = N
6.Hard
+ + + + + +− − − − − −e⁻1.5 × 10⁷ m/s3 cmE = 2200 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1.5 × 10⁷ m/s. The plates are 3 cm long and the field between them is 2200 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 = 1.5 × 10⁷ m/sL = 3 cmE = 2200 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 24.97 N
  2. 2. r = 18.96 cm
  3. 3. F = 4.195 N
  4. 4. E = 2.636 × 10⁶ N/C
  5. 5. F = 27.49 N
  6. 6. y = 0.7738 mm

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