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
−−8 µC−−6 µCr = 3 cm

Two point charges of −8 µC and −6 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = −6 µCr = 3 cm
F = N
2.Easy
+q₁+q₂r

Two point charges repel each other with a force of 6 N. The first charge is halved and the distance between the charges is tripled. Find the new force F′.

F = 6 Nq₁′ = 0.5·q₁r′ = 3·r
F′ = N
3.Medium
++8 µC++1 µCP10 cm

A charge of +8 µC and a charge of +1 µC are 10 cm apart. Point P lies on the line between them, 4 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = +1 µCr1 = 4 cmr2 = 6 cm
E = N/C
4.Medium
++8 µC−−2 µCP30 cm

A charge of +8 µC and a charge of −2 µC are 30 cm apart. Point P lies on the line between them, 12 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = −2 µCr1 = 12 cmr2 = 18 cm
E = N/C
5.Hard
10 cm8 cm+q1​ = +1 µC+q3​ = +4 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 1 µC is 10 cm from it along one side and q₂ = 6 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 6 µCq3 = 4 µCr13 = 10 cmr23 = 8 cm
F = N
6.Hard
+ + + + + +− − − − − −e⁻1.5 × 10⁷ m/s6 cmE = 2100 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1.5 × 10⁷ m/s. The plates are 6 cm long and the field between them is 2100 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 = 1.5 × 10⁷ m/sL = 6 cmE = 2100 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 479.5 N
  2. 2. F′ = 0.3333 N
  3. 3. E = 4.245 × 10⁷ N/C
  4. 4. E = 5.549 × 10⁶ N/C
  5. 5. F = 33.9 N
  6. 6. y = 2.955 mm

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