1. The problem statement, all variables and given/known data A copper wire with cross-sectional area S=2.5 mm^2 is bent to make three sides of a square frame that can pivot about the axis 00' as shown below. The wire is located in a uniform vertical magnetic field B. If upon passing a current I=16 milliAmperes through the wire, the wire deflects by an angle Θ= 0 degrees, find value of B (in SI units). 2. Relevant equations F = Force, measured in newtons I = current in wire, measured in amperes B = magnetic field vector, measured in teslas = vector cross product L = a vector, whose magnitude is the length of wire (measured in metres), and whose direction is along the wire, aligned with the direction of conventional current flow. 3. The attempt at a solution I can't seem to find what r and the unit vector for r is. Any hints? Or am I looking at this in the wrong way?