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
++6 µC−−6 µCr = 15 cm

Two point charges of +6 µC and −6 µC are 15 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 = 15 cm
F = N
2.Easy
−−4 µC−−6 µCr = 5 cm

Two point charges of −4 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 = −4 µCq2 = −6 µCr = 5 cm
F = N
3.Medium
++8 µC++10 µCP60 cm

A charge of +8 µC and a charge of +10 µC are 60 cm apart. Point P lies on the line between them, 36 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = +10 µCr1 = 36 cmr2 = 24 cm
E = N/C
4.Medium
−−8 µC++5 µC++3 µC10 cm + 30 cm

Three point charges lie on a straight line: −8 µC on the left, +3 µC on the right 40 cm away, and +5 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 = −8 µCqR = +3 µCqM = +5 µCrL = 10 cmrR = 30 cm
F = N
5.Hard
+−P2 × 4 cm3 cm+10 µC−10 µC

Charges of +10 µC and −10 µC are 8 cm apart. Point P lies 3 cm from the midpoint between them, on the perpendicular bisector. Find the magnitude of the electric field E at P. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = −10 µCd = 8 cmh = 3 cm
E = N/C
6.Hard
+ + + + + +− − − − − −e⁻5 × 10⁷ m/s6 cmE = 4200 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 5 × 10⁷ m/s. The plates are 6 cm long and the field between them is 4200 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 = 5 × 10⁷ m/sL = 6 cmE = 4200 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 14.38 N
  2. 2. F = 86.3 N
  3. 3. E = 1.006 × 10⁶ N/C
  4. 4. F = 37.46 N
  5. 5. E = 5.754 × 10⁷ N/C
  6. 6. y = 0.5318 mm

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