A straight wire of length L and carrying a curretn I stays suspended horizontally in mid air in a region where there is a uniform magnetic field `vecB`. The linear mass density of the wire is `lambda`. Obtain the magnitude and direction of this magnitude field.

Explanation

Magnitude field `vecB` should be such that force acting on current carrying conductor due to it acts vertically upward and just balances the weight of the conductor so that conductor remains freely suspended in mid air.
`:. BLI = mg = lambda L g " " [ :. m = lambda L` = mass of wire]
`implies B = (lambda g)/I`
Keeping in mind Fleming.s left hand rule, we can say that `vecB` must act horizontally in a direction perpendicular to the wire carrying current.