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?

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,

Therefore,

Image attached for better understanding of the problem.

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

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