Translated 9.2.10-9.2.17

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+ <h3 id="back-link"><a href="../../#9.2">$\leftarrow$Back</a></h3>
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+ <h3> Statement </h3>
+ <p>
+ $9.2.13.$ A long straight wire with current $I$ has a section in the form of a semicircle of radius $R$. Determine the magnetic field induction at the center of the semicircle.
+</p>
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+ <figcaption>
+ For problem $9.2.13$
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+<p>
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+ <h3>Solution</h3>
+ <p>
+ Let's write down the expression for the induction of a section of wire
+$$ d\vec B = \frac{\mu_0 [\vec{(Idx)}\times \vec{R}]}{4\pi R^3} $$
+We find the modulus of the vector $d\vec B$ by transforming the vector product
+$$ dB = \frac{\mu_0 Idx}{4\pi R^2}\sin\alpha $$
+Where $\alpha$ is the angle between the radius vector and the direction of the current element. Given that they coincide, then $\alpha = 0$:
+$$ \sin\alpha = 0\Rightarrow dB = 0 $$
+For a straight section of wire, then such a design creates a field similar to the field of the semicircle, which we already calculated in <a href="../9.2.11">9.2.11</a>
+$$ \boxed{B = \frac{\mu_0 I}{4R}} $$
+
+ </p>
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+ <h4>Answer</h4>
+ <p>
+ $$B=\frac{\mu_0 I}{4R}$$
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