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. The magnitude of B (in tesla) is (assume `g=9.9 ms^(-2)`)

Options

A. 2
B. `1.5`
C. `0.55`
D. `0.66`

Answer

D

Explanation

Magnetic force on a straight wire,
`F_(m)=IlBsin theta = IlBsin 90^(@)=BIl`.
Weight of a straight wire, W = mg
Since `F_(m)=W` or, `BIl=mg`
`therefore B=(mg)/(Il)=(200xx10^(-3)xx9.9)/(2xx1.5)=0.66` tesla.