A straight wire of mass 200 g and length 1.5 m carries a current of 2 A. It is suspended in mid-air by a uniform horizontal magnetic field B. What is the magnitude of the magnetic field?

Options

A. `2`
B. `1*5`
C. `0*55`
D. `0*65`

Answer

D

Explanation

Here, `m=200g=200xx10^-3kg`, `l=1*5m`,
`I=2A`, `g=9*8m//s^2`, `theta=90^@`
Force on current carrying conductor in mag. field is given by `F=IlB sin theta=IlBsin 90^@=IlB`
Weight `W=mg=200xx10^-3xx9*8N`
As it is suspended in mid air, So `W=F`
`mg=IlB`
or `B=(mg)/(Il)=(200xx10^-3xx9*8)/(2xx1*5)=0*65T`