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−−1 µCr = 12 cm

Two point charges of −6 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 = −6 µCq2 = −1 µCr = 12 cm
F = N
2.Easy
+q₁+q₂r

Two point charges repel each other with a force of 58 N. The first charge is halved and the distance between the charges is tripled. Find the new force F′.

F = 58 Nq₁′ = 0.5·q₁r′ = 3·r
F′ = N
3.Medium
++3 µC++10 µCP20 cm

A charge of +3 µC and a charge of +10 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 = +3 µCq2 = +10 µCr1 = 15 cmr2 = 5 cm
E = N/C
4.Medium
++6 µC++10 µCP60 cm

A charge of +6 µC and a charge of +10 µC are 60 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 = +6 µCq2 = +10 µCr1 = 15 cmr2 = 45 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻2 × 10⁷ m/s5 cmE = 3800 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2 × 10⁷ m/s. The plates are 5 cm long and the field between them is 3800 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 = 2 × 10⁷ m/sL = 5 cmE = 3800 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
++P2 × 3 cm3 cm+8 µC+8 µC

Charges of +8 µC and +8 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 = +8 µCq2 = +8 µCd = 6 cmh = 3 cm
E = N/C

Answer key

  1. 1. F = 3.746 N
  2. 2. F′ = 3.222 N
  3. 3. E = 3.476 × 10⁷ N/C
  4. 4. E = 1.953 × 10⁶ N/C
  5. 5. y = 2.088 mm
  6. 6. E = 5.651 × 10⁷ N/C

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