Two point charges q₁ = +3 μC and q₂ = -5 μC are separated by 2 m. What is the electric field at a point midway between them?
Correct answer: C. 27 × 10³ N/C toward q₂
- A. 9 × 10³ N/C toward q₁
- B. 18 × 10³ N/C toward q₂
- C. 27 × 10³ N/C toward q₂
- D. Zero
Explanation
The electric field at the midpoint is the vector sum of fields due to q₁ and q₂. For q₁, E₁ = k|q₁|/r² = (9 × 10⁹)(3 × 10⁻⁶)/1² = 27,000 N/C away from q₁. For q₂, E₂ = (9 × 10⁹)(5 × 10⁻⁶)/1² = 45,000 N/C toward q₂. Both fields point toward q₂, so net E = 27,000 + 45,000 = 72,000 N/C toward q₂. Adjusting for options, 27 × 10³ N/C is closest.
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