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−−1 µCr = 5 cm

Two point charges of +8 µC and −1 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +8 µCq2 = −1 µCr = 5 cm
F = N
2.Easy
+q₁+q₂r

Two point charges repel each other with a force of 30 N. The first charge is tripled and the distance between the charges is doubled. Find the new force F′.

F = 30 Nq₁′ = 3·q₁r′ = 2·r
F′ = N
3.Medium
++5 µC−−6 µCP10 cm

A charge of +5 µC and a charge of −6 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 = +5 µCq2 = −6 µCr1 = 4 cmr2 = 6 cm
E = N/C
4.Medium
−−1 µC++2 µCr = 40 cm

Two identical small metal spheres carry charges of −1 µC and +2 µC. They are touched together and then put back 40 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = +2 µCr = 40 cm
F = N
5.Hard
8 cm5 cm+q1​ = +2 µC+q3​ = +6 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 2 µC is 8 cm from it along one side and q₂ = 6 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 6 µCq3 = 6 µCr13 = 8 cmr23 = 5 cm
F = N
6.Hard
+−P2 × 3 cm8 cm+4 µC−4 µC

Charges of +4 µC and −4 µC are 6 cm apart. Point P lies 8 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 = +4 µCq2 = −4 µCd = 6 cmh = 8 cm
E = N/C

Answer key

  1. 1. F = 28.77 N
  2. 2. F′ = 22.5 N
  3. 3. E = 4.308 × 10⁷ N/C
  4. 4. F = 0.01405 N
  5. 5. F = 130.5 N
  6. 6. E = 3.459 × 10⁶ N/C

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