A force of 2.5\cdot 10^{-7} N acts on a unit of length of a straight long wire with current from the side of a second wire with the same current. The distance between the wires is 1 m, the current in the wires is 1 A. What is the magnetic permeability of this medium?

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    <h3 id="back-link"><a href="/#9.2">$\leftarrow$Back</a></h3>

    <h3> Statement </h3>
    <p>
        $9.2.4.$ A force of $2.5\cdot 10^{-7}$ N acts on a unit of length of a straight long wire with current from the side of a second wire with the same current. The distance between the wires is $1$ m, the current in the wires is 1 A. What is the magnetic permeability of this medium?
    </p>

    <h3>Solution</h3>
    <p>
        Magnetic induction of one wire with current $I$

$$B = \frac{\mu_0 \mu I}{2\pi R}$$
The force acting from the magnetic field $B$ on a piece of wire $\Delta l$ with a current of $I$
$$F = BI\Delta l = \frac{\mu_0 \mu I^2 \Delta l }{2\pi R}$$
Where do we express the magnetic permeability of the medium?
$$\boxed{\mu = \frac{2\pi F R}{\mu_0 I^2 \Delta l } = 1.25}$$

    </p>

    <h4>Answer</h4>
    <p>
        $$\mu = 1.25$$
    </p>
	<p style="text-align: right; font-style: italic; font-size: 14;">
      Andrei Yersh<br>
    </p>

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