Charges of +2.0 μC and −2.0 μC are 0.20 m apart in air. What is the electric field at the midpoint between them (k = 9.0 × 10⁹ N m² C⁻²)?
Correct answer C. 3.6 × 10⁶ N/C
Explanation
Each charge gives E = kq/r² = 9.0 × 10⁹ × 2.0 × 10⁻⁶ / 0.10² = 1.8 × 10⁶ N/C. Both fields point towards the negative charge, so they add to 3.6 × 10⁶ N/C.
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