Question

The distance between a north pole of strength $6\times {10}^{-3}Am$ and south pole of strength $8\times {10}^{-3}Am$ is $10cm$. The poles are separated in air. The force between them :

• A. $4.8\times {10}^{-11}N$
• B. $24\times {10}^{-11}N$
• C. $48\times {10}^{-11}N$
• D. $24\times {10}^{-12}N$

Answer 1

The correct option is C $48\times {10}^{-11}N$

$F=\frac{{\mu }_0}{4\pi }\frac{m_1{m}_2}{r^2}={10}^{-7}\times (6\times {10}^{-3})\times (8\times {10}^{-3})/(0.1{)}^2=48\times {10}^{-11}N$