Question:

A circular coil of $300$ turns and diameter $14\, cm$ carries a current of $15 \,A$. The magnitude of magnetic moment associated with the loop is

Updated On: Jun 23, 2023

$51.7\, J\, T^{-1}$
$69.2\, J\, T^{-1}$
$38.6\, J\, T^{-1}$
$19.5\, J\, T^{-1}$

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The Correct Option is B

Solution and Explanation

Here, $N = 300$, $I = 15 \,A$, $r = 7 \,cm = 7 \times 10^{-2} \,m$ $\therefore\quad M = NIA = NI \times \pi r^{2}$ $= 300 \times 15 \times 3.14 \times \left(7 \times 10^{-2}\right)^{2} = 69.2\, J \,T^{-1}$

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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.

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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.