SSE JE Electrical Engineering 10 Dec 2020 Papers

Question : 118 of 200

Marks: +1, -0

Two magnetic poles are located 5 cm apart in air. If each pole has a strength of 5 mWb, find the force of repulsion between them.

Solution:

Force of repulsion is given by

\F={\µ\m_1\m_2}/{4\π\d^2}

B = 5 mWb.

\B= \μ \H

\H = \B / \μ

\m_1 = \m_2 = \H = \B / \μ

∴\F ={ \B ^{2}}/{4 \π \µ\d ^{2}}

\µ= \permittivity =4 \π×10^{-7}

\F =(5 ×10^{-3})^{2} /(4 ×\π×4 \π×10^{-7} ×25 ×10^{-4})

=6250/\π^2\N

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