4.9 A square coil of side 10 cm consists of 20 turns and carries a current of 12 A. The coil is suspended vertically and the normal to the plane of the coil makes an angle of 30º with the direction of a uniform horizontal magnetic field of magnitude 0.80 T. What is the magnitude of torque experienced by the coil?

<p><strong>4.9 </strong>Length of a side of the square coil, l = 10 cm = 0.1 m</p><p>Current flowing through the coil, I = 12 A</p><p>Number of turns of the coil, n = 20</p><p>Angle made by the plane of the coil with magnetic field,<span contenteditable="false"> <math> <mi>θ</mi> </math> </span> = 30<span contenteditable="false"> <math> <mo>°</mo> </math> </span></p><p>Strength of the magnetic field, B = 0.80 T</p><p>Magnitude of the magnetic torque experienced by the coil in the magnetic field is given by,</p><p><span contenteditable="false"> <math> <mi>τ</mi> </math> </span>= nBIA<span contenteditable="false"> <math> <mrow> <mrow> <mi mathvariant="normal">sin</mi> </mrow> <mo>?</mo> <mrow> <mi>θ</mi> </mrow> </mrow> </math> </span>, where A = Area of the square coil = 0.1<span contenteditable="false"> <math> <mo>×</mo> <mn>0.1</mn> <mo>=</mo> <mn>0.01</mn> <mi> </mi> <msup> <mrow> <mrow> <mi>m</mi> </mrow> </mrow> <mrow> <mrow> <mn>2</mn> </mrow> </mrow> </msup> </math> </span></p><p><span contenteditable="false"> <math> <mi>τ</mi> <mo>=</mo> <mn>20</mn> <mo>×</mo> <mn>0.8</mn> <mo>×</mo> <mn>12</mn> <mo>×</mo> <mn>0.01</mn> <mo>×</mo> <mrow> <mrow> <mi mathvariant="normal">sin</mi> </mrow> <mo>?</mo> <mrow> <mn>30</mn> <mo>°</mo> </mrow> </mrow> </math> </span>= 0.96 Nm</p>

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