1.Easy
Find the magnitude of the electric field E at a distance of 3 cm from a point charge of −40 nC. Use k = 8.99 × 10⁹ N·m²/C².
q = −40 nCr = 3 cm
E = N/C
Coulomb’s law & electric fields worksheet with answers
2.Easy
An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2800 N/C. Ignoring gravity, find the magnitude of its acceleration a.
E = 2800 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
Charges of +4 µC and +1 µC are 30 cm apart. At what distance x from the +4 µC charge, on the line between them, is the electric field zero?
q1 = +4 µCq2 = +1 µCd = 30 cm
x = cm
4.Medium
A charge of +5 µC and a charge of +1 µC are 20 cm apart. Point P lies on the line between them, 12 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +5 µCq2 = +1 µCr1 = 12 cmr2 = 8 cm
E = N/C
5.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 5 µC is 5 cm from it along one side and q₂ = 10 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 5 µCq2 = 10 µCq3 = 4 µCr13 = 5 cmr23 = 5 cm
F = N
6.Hard
Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 20 cm long. They are given equal charges and each thread settles at 15° from the vertical. Use g = 9.81 m/s². Find the charge q on each ball in nC. Use k = 8.99 × 10⁹ N·m²/C².
m = 1 gL = 20 cmθ = 15°g = 9.81 m/s²
q = nC
Answer key
- 1. E = 399556 N/C
- 2. a = 4.924 × 10¹⁴ m/s²
- 3. x = 20 cm
- 4. E = 1.717 × 10⁶ N/C
- 5. F = 160.8 N
- 6. q = 55.98 nC
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