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.

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1.Easy
+ + + + + +− − − − − −e⁻E = 1000 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 1000 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 1000 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
2.Easy
++1 µC++1 µCr = ?

Point charges of +1 µC and +1 µC exert a force of 20 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = +1 µCF = 20 N
r = cm
3.Medium
−−8 µC−−6 µC−−4 µC15 cm + 5 cm

Three point charges lie on a straight line: −8 µC on the left, −4 µC on the right 20 cm away, and −6 µC between them, 15 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 = −8 µCqR = −4 µCqM = −6 µCrL = 15 cmrR = 5 cm
F = N
4.Medium
−−10 µC++6 µC++6 µC30 cm + 10 cm

Three point charges lie on a straight line: −10 µC on the left, +6 µC on the right 40 cm away, and +6 µC between them, 30 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 = −10 µCqR = +6 µCqM = +6 µCrL = 30 cmrR = 10 cm
F = N
5.Hard
6 cm10 cm+q1​ = +2 µC+q3​ = +2 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 2 µC is 6 cm from it along one side and q₂ = 5 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 5 µCq3 = 2 µCr13 = 6 cmr23 = 10 cm
F = N
6.Hard
3 cm6 cm+q1​ = +5 µC+q3​ = +6 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 5 µC is 3 cm from it along one side and q₂ = 4 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 5 µCq2 = 4 µCq3 = 6 µCr13 = 3 cmr23 = 6 cm
F = N

Answer key

  1. 1. a = 1.759 × 10¹⁴ m/s²
  2. 2. r = 2.12 cm
  3. 3. F = 67.13 N
  4. 4. F = 38.36 N
  5. 5. F = 13.44 N
  6. 6. F = 305.6 N

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