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
−−3 µC−−4 µCr = 5 cm

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

q1 = −3 µCq2 = −4 µCr = 5 cm
F = N
2.Easy
++1 µC++8 µCr = 12 cm

Two point charges of +1 µC and +8 µC are 12 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 = 12 cm
F = N
3.Medium
++3 µC−−1 µCP60 cm

A charge of +3 µC and a charge of −1 µC are 60 cm apart. Point P lies on the line between them, 24 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −1 µCr1 = 24 cmr2 = 36 cm
E = N/C
4.Medium
−−1 µC−−4 µC++3 µC24 cm + 16 cm

Three point charges lie on a straight line: −1 µC on the left, +3 µC on the right 40 cm away, and −4 µC between them, 24 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 = +3 µCqM = −4 µCrL = 24 cmrR = 16 cm
F = N
5.Hard
+ + + + + +− − − − − −e⁻2.5 × 10⁷ m/s4 cmE = 1900 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2.5 × 10⁷ m/s. The plates are 4 cm long and the field between them is 1900 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 = 2.5 × 10⁷ m/sL = 4 cmE = 1900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
6 cm4 cm+q1​ = +4 µC+q3​ = +1 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 4 µC is 6 cm from it along one side and q₂ = 5 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 5 µCq3 = 1 µCr13 = 6 cmr23 = 4 cm
F = N

Answer key

  1. 1. F = 43.15 N
  2. 2. F = 4.994 N
  3. 3. E = 537596 N/C
  4. 4. F = 4.838 N
  5. 5. y = 0.4277 mm
  6. 6. F = 29.82 N

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