CSCAPrep
Reviewed CSCA Physics question · Standard

真空中两个点电荷，电荷量分别为 +2×10⁻⁶ C 和 -4×10⁻⁶ C，相距0.3 m。已知静电力常量 k = 9×10⁹ N·m²/C²，求它们之间的静电力大小。

  1. 0.2 N
  2. 0.4 N
  3. 0.8 N
  4. 1.6 N
Show the answer and explanation

Correct answer

C. 0.8 N

Principle or equation

库仑定律：F = k |q1 q2| / r²。

Why this answer is correct

F = 9×10⁹ × (2×10⁻⁶ × 4×10⁻⁶) / (0.3)² = 9×10⁹ × 8×10⁻¹² / 0.09 = 72×10⁻³ / 0.09 = 0.8 N。

Example

若距离为0.6 m，则力变为0.2 N（距离加倍，力减为四分之一）。

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