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.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
++1 µC−−8 µCr = 20 cm

Two point charges of +1 µC and −8 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = −8 µCr = 20 cm
F = N
2.Easy
++5 µC++3 µCr = 10 cm

Two point charges of +5 µC and +3 µC are 10 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 = 10 cm
F = N
3.Medium
++8 µC++6 µCr = 10 cm

Two identical small metal spheres carry charges of +8 µC and +6 µC. They are touched together and then put back 10 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +8 µCq2 = +6 µCr = 10 cm
F = N
4.Medium
++5 µC−−8 µCP50 cm

A charge of +5 µC and a charge of −8 µC are 50 cm apart. Point P lies on the line between them, 25 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = −8 µCr1 = 25 cmr2 = 25 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻2 × 10⁷ m/s6 cmE = 3000 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2 × 10⁷ m/s. The plates are 6 cm long and the field between them is 3000 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 × 10⁷ m/sL = 6 cmE = 3000 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
L = 40 cm10°qq

Two identical small balls, each of mass 2 g, hang from the same point on insulating threads 40 cm long. They are given equal charges and each thread settles at 10° from the vertical. Use g = 9.81 m/s². Find the charge q on each ball in nC. Use k = 8.99 × 10⁹ N·m²/C².

m = 2 gL = 40 cmθ = 10°g = 9.81 m/s²
q = nC

Answer key

  1. 1. F = 1.798 N
  2. 2. F = 13.48 N
  3. 3. F = 44.05 N
  4. 4. E = 1.87 × 10⁶ N/C
  5. 5. y = 2.374 mm
  6. 6. q = 86.18 nC

Full step-by-step solutions: practise this topic on examproblems.com.