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++2 µCr = 6 cm

Two point charges of −1 µC and +2 µC are 6 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = +2 µCr = 6 cm
F = N
2.Easy
++10 µC++10 µCr = 8 cm

Two point charges of +10 µC and +10 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = +10 µCr = 8 cm
F = N
3.Medium
++2 µC−−5 µCP30 cm

A charge of +2 µC and a charge of −5 µC are 30 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = −5 µCr1 = 7.5 cmr2 = 22.5 cm
E = N/C
4.Medium
++10 µC++3 µC−−4 µC16 cm + 24 cm

Three point charges lie on a straight line: +10 µC on the left, −4 µC on the right 40 cm away, and +3 µC between them, 16 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 = +10 µCqR = −4 µCqM = +3 µCrL = 16 cmrR = 24 cm
F = N
5.Hard
+ + + + + +− − − − − −e⁻2.5 × 10⁷ m/s8 cmE = 1900 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 1900 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 = 1900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
+ + + + + +− − − − − −e⁻3 × 10⁷ m/s3 cmE = 4700 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 3 × 10⁷ m/s. The plates are 3 cm long and the field between them is 4700 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 × 10⁷ m/sL = 3 cmE = 4700 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 4.994 N
  2. 2. F = 140.5 N
  3. 3. E = 4.084 × 10⁶ N/C
  4. 4. F = 12.41 N
  5. 5. y = 1.711 mm
  6. 6. y = 0.4133 mm

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