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++5 µCr = 12 cm

Two point charges of −6 µC and +5 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +5 µCr = 12 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 2500 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2500 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2500 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
−−4 µC−−6 µC++5 µC15 cm + 15 cm

Three point charges lie on a straight line: −4 µC on the left, +5 µC on the right 30 cm away, and −6 µC between them, 15 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 = +5 µCqM = −6 µCrL = 15 cmrR = 15 cm
F = N
4.Medium
++10 µC++4 µCE = 030 cm

Charges of +10 µC and +4 µC are 30 cm apart. At what distance x from the +10 µC charge, on the line between them, is the electric field zero?

q1 = +10 µCq2 = +4 µCd = 30 cm
x = cm
5.Hard
6 cm5 cm+q1​ = +10 µC+q3​ = +2 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 10 µC is 6 cm from it along one side and q₂ = 10 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 10 µCq3 = 2 µCr13 = 6 cmr23 = 5 cm
F = N
6.Hard
+ + + + + +− − − − − −e⁻2.5 × 10⁷ m/s8 cmE = 3100 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 3100 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 = 3100 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 18.73 N
  2. 2. a = 4.397 × 10¹⁴ m/s²
  3. 3. F = 21.58 N
  4. 4. x = 18.38 cm
  5. 5. F = 87.56 N
  6. 6. y = 2.791 mm

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