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
−−5 µC−−6 µCr = 5 cm

Two point charges of −5 µC and −6 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −5 µCq2 = −6 µCr = 5 cm
F = N
2.Easy
−−3 µC++5 µCr = 4 cm

Two point charges of −3 µC and +5 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −3 µCq2 = +5 µCr = 4 cm
F = N
3.Medium
++5 µC++10 µC−−10 µC5 cm + 15 cm

Three point charges lie on a straight line: +5 µC on the left, −10 µC on the right 20 cm away, and +10 µC between them, 5 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 = +5 µCqR = −10 µCqM = +10 µCrL = 5 cmrR = 15 cm
F = N
4.Medium
++5 µC++1 µCP30 cm

A charge of +5 µC and a charge of +1 µC are 30 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 = +5 µCq2 = +1 µCr1 = 15 cmr2 = 15 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻2 × 10⁷ m/s6 cmE = 3300 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 3300 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 = 3300 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
10 cm3 cm+q1​ = +8 µC+q3​ = +3 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 8 µC is 10 cm from it along one side and q₂ = 4 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 4 µCq3 = 3 µCr13 = 10 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 107.9 N
  2. 2. F = 84.28 N
  3. 3. F = 219.8 N
  4. 4. E = 1.598 × 10⁶ N/C
  5. 5. y = 2.612 mm
  6. 6. F = 121.8 N

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