A straight wire of mass 400 g and length 2m carries a current of 2A. It is suspended in mid air by a uniform horizontal field B. What is the magnitude of the magnetic field ?

Explanation

`F_(m)` is the magnetic force acting on the wire which acts upwards and balances mg. Thus, `Bil sin theta = mg`
`theta = 90^(@)`
`B = (0.4 xx 9.8)/(2 xx 2 xx sin 90^(@))`
`rArr B = 0.98 T`