Question:

Two identical thin bar magnets are placed mutually at right angles such that the north pole of one touches the south pole of the other. The length and the pole strength of each bar are $I$ and $m$. The resultant magnetic moment of the system is :

Updated On: Jun 23, 2023
  • $ml$
  • $\sqrt{2}\,ml$
  • $\sqrt{3}\,ml$
  • $2\,ml$
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The Correct Option is B

Solution and Explanation

Resultant magnetic moment is given by M = $\sqrt{M_1^2 + M_2^2} = \sqrt{(ml)^2 + (ml)^2} = ml \sqrt{2} $ = $\sqrt{2} ml$
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Concepts Used:

Magnetism & Matter

Magnets are used in many devices like electric bells, telephones, radio, loudspeakers, motors, fans, screwdrivers, lifting heavy iron loads, super-fast trains, especially in foreign countries, refrigerators, etc.

Magnetite is the world’s first magnet. This is also called a natural magnet.  Though magnets occur naturally, we can also impart magnetic properties to a substance. It would be an artificial magnet in that case.

Read More: Magnetism and Matter

Some of the properties of the magnetic field lines are:

  • The lines and continuous and outside the magnet, the field lines originate from the North pole and terminate at the South pole
  • They form closed loops traversing inside the magnet. 
  • But here the lines seem to originate from the South pole and terminate at the North pole to form closed loops.
  • More number of close lines indicate a stronger magnetic field
  • The lines do not intersect each other
  • The tangent drawn at the field line gives the direction of the field at that point.