A straight wire of mass 200 g and length 1.5 m carries a current of 2A. It is suspended in mid-air by a uniform horizontal magnetic field B. The magnitude of B (in tesla) is (assume `g = 9.8 ms^(-2)`)

Options

A. `2`
B. `1.5`
C. `0.55`
D. `0.65`

Answer

D

Explanation

Magnetic force on straight wire
`F = Bil sin theta = Bil sin 90^@ - Bil`
For equilibrium of wire in mid-air,
`F = mg`
`Bil = mg `
`therefore B = (mg)/(Bil) = (200 xx 10^(-3) xx 9.8)/(2 xx 1.5) = 0.65 T`