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

Find the magnitude of the electric field E at a distance of 25 cm from a point charge of +40 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +40 nCr = 25 cm

E = N/C

2.Easy

Two point charges repel each other with a force of 26 N. The first charge is halved and the distance between the charges is tripled. Find the new force F′.

F = 26 Nq₁′ = 0.5·q₁r′ = 3·r

F′ = N

3.Medium

Charges of +10 µC and +5 µC are 60 cm apart. At what distance x from the +10 µC charge, on the line between them, is the electric field zero?

q₁ = +10 µCq₂ = +5 µCd = 60 cm

x = cm

4.Medium

A charge of +10 µC and a charge of −1 µC are 50 cm apart. Point P lies on the line between them, 20 cm from the first charge. Find the magnitude of the electric field E at P.

q₁ = +10 µCq₂ = −1 µCr₁ = 20 cmr₂ = 30 cm

E = N/C

5.Hard

Charges of +10 µC and +10 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 = +10 µCq₂ = +10 µCd = 6 cmh = 3 cm

E = N/C

6.Hard

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 1 µC is 5 cm from it along one side and q₂ = 1 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q₁ = 1 µCq₂ = 1 µCq₃ = 4 µCr₁₃ = 5 cmr₂₃ = 10 cm

F = N

Answer key

1. E = 5754 N/C
2. F′ = 1.444 N
3. x = 35.15 cm
4. E = 2.347 × 10⁶ N/C
5. E = 7.063 × 10⁷ N/C
6. F = 14.83 N

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