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
++1 µC++3 µCr = 25 cm

Two point charges of +1 µC and +3 µC are 25 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = +3 µCr = 25 cm
F = N
2.Easy
−−4 µC++5 µCr = 8 cm

Two point charges of −4 µC and +5 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −4 µCq2 = +5 µCr = 8 cm
F = N
3.Medium
++1 µC++4 µCE = 080 cm

Charges of +1 µC and +4 µC are 80 cm apart. At what distance x from the +1 µC charge, on the line between them, is the electric field zero?

q1 = +1 µCq2 = +4 µCd = 80 cm
x = cm
4.Medium
−−5 µC−−6 µCr = 50 cm

Two identical small metal spheres carry charges of −5 µC and −6 µC. They are touched together and then put back 50 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −5 µCq2 = −6 µCr = 50 cm
F = N
5.Hard
+ + + + + +− − − − − −e⁻4.5 × 10⁷ m/s8 cmE = 1700 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 4.5 × 10⁷ m/s. The plates are 8 cm long and the field between them is 1700 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 = 4.5 × 10⁷ m/sL = 8 cmE = 1700 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
+ + + + + +− − − − − −e⁻1 × 10⁷ m/s3 cmE = 1700 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 1 × 10⁷ m/s. The plates are 3 cm long and the field between them is 1700 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 × 10⁷ m/sL = 3 cmE = 1700 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm

Answer key

  1. 1. F = 0.4315 N
  2. 2. F = 28.09 N
  3. 3. x = 26.67 cm
  4. 4. F = 1.088 N
  5. 5. y = 0.4725 mm
  6. 6. y = 1.345 mm

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