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−−5 µCr = 3 cm

Two point charges of −6 µC and −5 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = −5 µCr = 3 cm
F = N
2.Easy
++3 µC−−3 µCr = 4 cm

Two point charges of +3 µC and −3 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 = −3 µCr = 4 cm
F = N
3.Medium
++3 µC++10 µCE = 030 cm

Charges of +3 µC and +10 µC are 30 cm apart. At what distance x from the +3 µC charge, on the line between them, is the electric field zero?

q1 = +3 µCq2 = +10 µCd = 30 cm
x = cm
4.Medium
++4 µC++6 µCP30 cm

A charge of +4 µC and a charge of +6 µC are 30 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +4 µCq2 = +6 µCr1 = 7.5 cmr2 = 22.5 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻2.5 × 10⁷ m/s3 cmE = 2800 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 2.5 × 10⁷ m/s. The plates are 3 cm long and the field between them is 2800 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 = 2.5 × 10⁷ m/sL = 3 cmE = 2800 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
8 cm5 cm+q1​ = +6 µC+q3​ = +2 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 6 µC is 8 cm from it along one side and q₂ = 2 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 2 µCq3 = 2 µCr13 = 8 cmr23 = 5 cm
F = N

Answer key

  1. 1. F = 299.7 N
  2. 2. F = 50.57 N
  3. 3. x = 10.62 cm
  4. 4. E = 5.327 × 10⁶ N/C
  5. 5. y = 0.3546 mm
  6. 6. F = 22.16 N

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