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
−−6 µC++2 µCr = 2 cm

Two point charges of −6 µC and +2 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +2 µCr = 2 cm
F = N
2.Easy
−−1 µC−−5 µCr = 15 cm

Two point charges of −1 µC and −5 µC are 15 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = −5 µCr = 15 cm
F = N
3.Medium
++4 µC++1 µC−−10 µC10 cm + 30 cm

Three point charges lie on a straight line: +4 µC on the left, −10 µC on the right 40 cm away, and +1 µC between them, 10 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 = +4 µCqR = −10 µCqM = +1 µCrL = 10 cmrR = 30 cm
F = N
4.Medium
++8 µC−−3 µCP30 cm

A charge of +8 µC and a charge of −3 µC are 30 cm apart. Point P lies on the line between them, 12 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = −3 µCr1 = 12 cmr2 = 18 cm
E = N/C
5.Hard
++P2 × 5 cm6 cm+1 µC+1 µC

Charges of +1 µC and +1 µC are 10 cm apart. Point P lies 6 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 = 10 cmh = 6 cm
E = N/C
6.Hard
4 cm8 cm+q1​ = +4 µC+q3​ = +8 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 4 µC is 4 cm from it along one side and q₂ = 5 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 5 µCq3 = 8 µCr13 = 4 cmr23 = 8 cm
F = N

Answer key

  1. 1. F = 269.7 N
  2. 2. F = 1.998 N
  3. 3. F = 4.595 N
  4. 4. E = 5.827 × 10⁶ N/C
  5. 5. E = 2.264 × 10⁶ N/C
  6. 6. F = 188.4 N

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