Translated 9.1.6-9.1.15

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+ <h3 id="back-link"><a href="../../#9.1">$\leftarrow$Back</a></h3>
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+ <h3> Statement </h3>
+ <p>
+ $9.1.13^*.$ A coil with a current flowing through its turns stands vertically on a plane. The total weight of the coil is $P$, the number of turns is $n$, the radius is $R$, and the current in the turns is $I$. At what induction of a uniform magnetic field directed horizontally will the coil overturn under the action of this field?
+ </p>
+
+ <h3>Solution</h3>
+ <p>
+ Moment of gravity for the coil relative to the edge of the coil:
+$$ M_{mg} = R\cdot mg = PR $$
+Moment of magnetic field forces:
+$$ M_B = n\cdot BSI = n\cdot \pi R^2BI $$
+In the equilibrium condition, the total moment of forces, taking into account the signs, is equal to zero
+$$ n\cdot \pi R^2BI = PR \Rightarrow \boxed{ B = \frac{P}{n\pi RI}} $$
+
+ </p>
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+ <h4>Answer</h4>
+ <p>
+ $$B = \frac{P}{n\pi RI}$$
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+ Andrei Yersh<br>
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