Question

An isolated unit north pole expending force of $2\times {10}^{-7}N$ when kept at a distance 1m from a magnetic pole in air. The strength of thr pole is:

• A. $2\times {10}^{7}A-m$
• B. $2A-m$
• C. $2\times {10}^{-11}A-m$
• D. $4Am$

Answer 1

Answer: (B)

$2A-m$

Given: force experienced,$F=2\ast {10}^{-7}N$

magnetic pole strength of north pole, $m_1=1A-m$

distance between north pole and magnetic pole is,$r=1m$

To Find: magnetic pole strength of magnetic pole is,$m_2=?$

Solution: as we know,

force experienced, $F=\frac{{\mu }_o}{4\pi }\ast \frac{m_1\ast m_2}{r^2}$

$m_2=F\ast \frac{4\pi }{{\mu }_o\ast m_1}\ast r^2$

$m_2=\frac{2\ast {10}^{-7}\ast {10}^7\ast 1}{1}$

$m_2=2A-m$