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 = 500 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 500 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 500 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
2.Easy
++5 µC−−10 µCr = 2 cm

Two point charges of +5 µC and −10 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +5 µCq2 = −10 µCr = 2 cm
F = N
3.Medium
++5 µC−−5 µCP20 cm

A charge of +5 µC and a charge of −5 µC are 20 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 = −5 µCr1 = 15 cmr2 = 5 cm
E = N/C
4.Medium
−−5 µC++5 µC++5 µC12 cm + 18 cm

Three point charges lie on a straight line: −5 µC on the left, +5 µC on the right 30 cm away, and +5 µC between them, 12 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 = +5 µCqM = +5 µCrL = 12 cmrR = 18 cm
F = N
5.Hard
3 cm4 cm+q1​ = +2 µC+q3​ = +1 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 2 µC is 3 cm from it along one side and q₂ = 10 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 10 µCq3 = 1 µCr13 = 3 cmr23 = 4 cm
F = N
6.Hard
++P2 × 6 cm5 cm+4 µC+4 µC

Charges of +4 µC and +4 µC are 12 cm apart. Point P lies 5 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 = 12 cmh = 5 cm
E = N/C

Answer key

  1. 1. a = 8.794 × 10¹³ m/s²
  2. 2. F = 1124 N
  3. 3. E = 1.998 × 10⁷ N/C
  4. 4. F = 22.54 N
  5. 5. F = 59.63 N
  6. 6. E = 7.548 × 10⁶ N/C

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