question_answer

A square cardboard of side ℓ and mass m is suspended from a horizontal axis XY as shown in figure. A single wire is would along the periphery of board and carrying a clockwise current I. At\[t=0\], a vertical downward magnetic field of induction B is switched on. Find the minimum value of B (in T) so that the board will be able to rotate up to horizontal level. (\[m=1kg,\text{ }I1\]amp, \[\ell =1\]metre)

Answer:

5.00