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
++4 µC++1 µCr = 12 cm

Two point charges of +4 µC and +1 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = +1 µCr = 12 cm
F = N
2.Easy
++4 µC++1 µCr = 2 cm

Two point charges of +4 µC and +1 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = +1 µCr = 2 cm
F = N
3.Medium
++10 µC−−2 µCr = 10 cm

Two identical small metal spheres carry charges of +10 µC and −2 µC. They are touched together and then put back 10 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = −2 µCr = 10 cm
F = N
4.Medium
++6 µC−−1 µCP50 cm

A charge of +6 µC and a charge of −1 µC are 50 cm apart. Point P lies on the line between them, 30 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +6 µCq2 = −1 µCr1 = 30 cmr2 = 20 cm
E = N/C
5.Hard
++P2 × 3 cm3 cm+1 µC+1 µC

Charges of +1 µC and +1 µC are 6 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 = +1 µCq2 = +1 µCd = 6 cmh = 3 cm
E = N/C
6.Hard
+ + + + + +− − − − − −e⁻1.5 × 10⁷ m/s3 cmE = 3900 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1.5 × 10⁷ m/s. The plates are 3 cm long and the field between them is 3900 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 = 1.5 × 10⁷ m/sL = 3 cmE = 3900 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 2.497 N
  2. 2. F = 89.9 N
  3. 3. F = 14.38 N
  4. 4. E = 824083 N/C
  5. 5. E = 7.063 × 10⁶ N/C
  6. 6. y = 1.372 mm

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