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
+ + + + + +− − − − − −e⁻E = 3800 N/C

A proton (charge 1.602 × 10⁻¹⁹ C, mass 1.673 × 10⁻²⁷ kg) is in a uniform electric field of 3800 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 3800 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 1.673 × 10⁻²⁷ kg
a = m/s²
2.Easy
++6 µC++2 µCr = 25 cm

Two point charges of +6 µC and +2 µC are 25 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 = 25 cm
F = N
3.Medium
++6 µC++8 µCE = 040 cm

Charges of +6 µC and +8 µC are 40 cm apart. At what distance x from the +6 µC charge, on the line between them, is the electric field zero?

q1 = +6 µCq2 = +8 µCd = 40 cm
x = cm
4.Medium
++5 µC++3 µCP50 cm

A charge of +5 µC and a charge of +3 µC are 50 cm apart. Point P lies on the line between them, 25 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +3 µCr1 = 25 cmr2 = 25 cm
E = N/C
5.Hard
+ + + + + +− − − − − −e⁻1.5 × 10⁷ m/s2 cmE = 2400 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 2 cm long and the field between them is 2400 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 = 2 cmE = 2400 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
+−P2 × 5 cm12 cm+5 µC−5 µC

Charges of +5 µC and −5 µC are 10 cm apart. Point P lies 12 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 = +5 µCq2 = −5 µCd = 10 cmh = 12 cm
E = N/C

Answer key

  1. 1. a = 3.639 × 10¹¹ m/s²
  2. 2. F = 1.726 N
  3. 3. x = 18.56 cm
  4. 4. E = 287680 N/C
  5. 5. y = 0.3752 mm
  6. 6. E = 2.046 × 10⁶ N/C

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