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
++10 µC++2 µCr = ?

Point charges of +10 µC and +2 µC exert a force of 1 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = +2 µCF = 1 N
r = cm
2.Easy
−−5 µC++8 µCr = 4 cm

Two point charges of −5 µC and +8 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −5 µCq2 = +8 µCr = 4 cm
F = N
3.Medium
++5 µC−−1 µCr = 40 cm

Two identical small metal spheres carry charges of +5 µC and −1 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 = +5 µCq2 = −1 µCr = 40 cm
F = N
4.Medium
++8 µC++3 µCE = 060 cm

Charges of +8 µC and +3 µC are 60 cm apart. At what distance x from the +8 µC charge, on the line between them, is the electric field zero?

q1 = +8 µCq2 = +3 µCd = 60 cm
x = cm
5.Hard
+ + + + + +− − − − − −e⁻3 × 10⁷ m/s6 cmE = 2400 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 3 × 10⁷ m/s. The plates are 6 cm long and the field between them is 2400 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 = 3 × 10⁷ m/sL = 6 cmE = 2400 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
L = 50 cm10°qq

Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 50 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 = 1 gL = 50 cmθ = 10°g = 9.81 m/s²
q = nC

Answer key

  1. 1. r = 42.4 cm
  2. 2. F = 224.7 N
  3. 3. F = 0.2247 N
  4. 4. x = 37.21 cm
  5. 5. y = 0.8442 mm
  6. 6. q = 76.17 nC

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