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
++3 µC++10 µCr = 4 cm

Two point charges of +3 µC and +10 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 = +10 µCr = 4 cm
F = N
2.Easy
−−5 µCPr = 10 cm

Find the magnitude of the electric field E at a distance of 10 cm from a point charge of −5 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −5 µCr = 10 cm
E = N/C
3.Medium
++1 µC++1 µC++8 µC12 cm + 8 cm

Three point charges lie on a straight line: +1 µC on the left, +8 µC on the right 20 cm away, and +1 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 = +1 µCqR = +8 µCqM = +1 µCrL = 12 cmrR = 8 cm
F = N
4.Medium
−−2 µC++5 µC++3 µC5 cm + 15 cm

Three point charges lie on a straight line: −2 µC on the left, +3 µC on the right 20 cm away, and +5 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 = −2 µCqR = +3 µCqM = +5 µCrL = 5 cmrR = 15 cm
F = N
5.Hard
++P2 × 4 cm3 cm+3 µC+3 µC

Charges of +3 µC and +3 µC are 8 cm apart. Point P lies 3 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 = +3 µCq2 = +3 µCd = 8 cmh = 3 cm
E = N/C
6.Hard
+−P2 × 3 cm5 cm+1 µC−1 µC

Charges of +1 µC and −1 µC are 6 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 = +1 µCq2 = −1 µCd = 6 cmh = 5 cm
E = N/C

Answer key

  1. 1. F = 168.6 N
  2. 2. E = 4.495 × 10⁶ N/C
  3. 3. F = 10.61 N
  4. 4. F = 41.95 N
  5. 5. E = 1.295 × 10⁷ N/C
  6. 6. E = 2.721 × 10⁶ N/C

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