Question

A vertical straight wire carrying an upward 26-A current exerts an attractive force per unit length of 7.3×10−4 N/m on a second parallel wire 7.5 cm away. What is the direction of the current in the second wire?

Answer 1

Answer:

The direction of current in the second wire will be upward.

Explanation:

We first need to find the direction of the magnetic field due to the first wire using the right-hand thumb rule.

Knowing that, one can easily find the direction of the second wire by using the right-hand rule.

The force per unit length on wire 2 due to wire 1 is given by,

$\frac{F}{\Delta L} =\frac{\mu_oI_1I_2}{2\pi r}$

Therefore,

$I_2=\frac{F}{\Delta L} \frac{2\pi r}{\mu_oI_1} =\frac{7.3\times10^{-4}\times 2\pi\times0.075}{1.256\times10^{-6}\times26} A=1.053A$

Image attached for better understanding of the problem.

(Source: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/wirfor.html)