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−−5 µCr = 25 cm

Two point charges of +1 µC and −5 µC are 25 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = −5 µCr = 25 cm
F = N
2.Easy
−−6 µC++6 µCr = 8 cm

Two point charges of −6 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 = −6 µCq2 = +6 µCr = 8 cm
F = N
3.Medium
++1 µC++6 µC−−10 µC12 cm + 18 cm

Three point charges lie on a straight line: +1 µC on the left, −10 µC on the right 30 cm away, and +6 µC between them, 12 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 = +1 µCqR = −10 µCqM = +6 µCrL = 12 cmrR = 18 cm
F = N
4.Medium
++5 µC++4 µCP40 cm

A charge of +5 µC and a charge of +4 µC are 40 cm apart. Point P lies on the line between them, 24 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +4 µCr1 = 24 cmr2 = 16 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻3.5 × 10⁷ m/s8 cmE = 2900 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 3.5 × 10⁷ m/s. The plates are 8 cm long and the field between them is 2900 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 = 3.5 × 10⁷ m/sL = 8 cmE = 2900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
5 cm10 cm+q1​ = +6 µC+q3​ = +4 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 6 µC is 5 cm from it along one side and q₂ = 10 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 10 µCq3 = 4 µCr13 = 5 cmr23 = 10 cm
F = N

Answer key

  1. 1. F = 0.7192 N
  2. 2. F = 50.57 N
  3. 3. F = 20.39 N
  4. 4. E = 624306 N/C
  5. 5. y = 1.332 mm
  6. 6. F = 93.5 N

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