Two point charges +3 × 10⁻⁸ C and −2 × 10⁻⁸ C are placed 15 cm apart o…

Question

Two point charges +3 × 10⁻⁸ C and −2 × 10⁻⁸ C are placed 15 cm apart on a line. Taking V(∞) = 0, the point on the line between them where V = 0 lies at a distance from the positive charge of

Accepted Answer

B. {'text': '9 cm', 'label': 'B'}

1. Let the zero-potential point be at distance x from +3 × 10⁻⁸ C and (15 − x) from −2 × 10⁻⁸ C.
2. V = k(3 × 10⁻⁸)/x + k(−2 × 10⁻⁸)/(15 − x) = 0.
3. ⇒ 3/x = 2/(15 − x) ⇒ 3(15 − x) = 2x ⇒ 45 = 5x ⇒ x = 9 cm.
4. (Note: a second zero exists at x = 45 cm, outside the segment; this question asked for the interior point.)
_Source: NCERT Class 12 Physics Part I, Ch 2 Example 2.2_

Answer

{'text': '5 cm', 'label': 'A'}

Answer

{'text': '12 cm', 'label': 'C'}

Answer

{'text': '6 cm', 'label': 'D'}