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

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

F = 26 Nq₁′ = 4·q₁r′ = 0.5·r

F′ = N

2.Easy

Find the magnitude of the electric field E at a distance of 8 cm from a point charge of +100 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +100 nCr = 8 cm

E = N/C

3.Medium

A charge of +4 µC and a charge of −8 µC are 60 cm apart. Point P lies on the line between them, 30 cm from the first charge. Find the magnitude of the electric field E at P.

q₁ = +4 µCq₂ = −8 µCr₁ = 30 cmr₂ = 30 cm

E = N/C

4.Medium

Charges of +10 µC and +6 µC are 30 cm apart. At what distance x from the +10 µC charge, on the line between them, is the electric field zero?

q₁ = +10 µCq₂ = +6 µCd = 30 cm

x = cm

5.Hard

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 8 µC is 3 cm from it along one side and q₂ = 6 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q₁ = 8 µCq₂ = 6 µCq₃ = 8 µCr₁₃ = 3 cmr₂₃ = 3 cm

F = N

6.Hard

Charges of +2 µC and −2 µC are 12 cm apart. Point P lies 10 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 = +2 µCq₂ = −2 µCd = 12 cmh = 10 cm

E = N/C

Answer key

1. F′ = 416 N
2. E = 140469 N/C
3. E = 1.199 × 10⁶ N/C
4. x = 16.91 cm
5. F = 799.1 N
6. E = 1.36 × 10⁶ N/C

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