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
−−5 µC++3 µCr = 20 cm

Two point charges of −5 µC and +3 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −5 µCq2 = +3 µCr = 20 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 1300 N/C

A proton (charge 1.602 × 10⁻¹⁹ C, mass 1.673 × 10⁻²⁷ kg) is in a uniform electric field of 1300 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 1300 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 1.673 × 10⁻²⁷ kg
a = m/s²
3.Medium
++2 µC++3 µCP60 cm

A charge of +2 µC and a charge of +3 µC are 60 cm apart. Point P lies on the line between them, 15 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = +3 µCr1 = 15 cmr2 = 45 cm
E = N/C
4.Medium
−−1 µC++4 µC++1 µC18 cm + 12 cm

Three point charges lie on a straight line: −1 µC on the left, +1 µC on the right 30 cm away, and +4 µC between them, 18 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 = +1 µCqM = +4 µCrL = 18 cmrR = 12 cm
F = N
5.Hard
+ + + + + +− − − − − −e⁻1 × 10⁷ m/s3 cmE = 4800 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1 × 10⁷ m/s. The plates are 3 cm long and the field between them is 4800 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 × 10⁷ m/sL = 3 cmE = 4800 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
++P2 × 4 cm6 cm+5 µC+5 µC

Charges of +5 µC and +5 µC are 8 cm apart. Point P lies 6 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 = +5 µCq2 = +5 µCd = 8 cmh = 6 cm
E = N/C

Answer key

  1. 1. F = 3.371 N
  2. 2. a = 1.245 × 10¹¹ m/s²
  3. 3. E = 665926 N/C
  4. 4. F = 3.607 N
  5. 5. y = 3.799 mm
  6. 6. E = 1.438 × 10⁷ N/C

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