A lifting device must just raise a steel bar vertically

MATHEMATICS · Single correct · ISC · Mathematics · Physics · Gravitation

Problem

A lifting device must just raise a

1.2\,\text{kg}

steel bar vertically. It uses a straight conductor

0.40\,\text{m}

long carrying a maximum safe current of

25\,\text{A}

in a uniform magnetic field that makes an angle of

60^{\circ}

with the conductor. Taking

g = 9.8\,\text{m\,s}^{-2}

, what minimum magnetic field strength is required? (a)

2.35\,\text{T}

(b)

0.68\,\text{T}

(c)

1.36\,\text{T}

(d)

1.18\,\text{T}