A uniform magnetic needle of strength of each pole is 98.1 amp, cm, is suspended from its centre by a thread. When a mass of 50 mg is loaded to its upper end, the needle becomes horizontal, then the vertical component of earth's magnetic induction is (g=981 cm//s^(2))

A uniform magnetic needle of strength of each pole is 98.1 amp, cm, is

1.	A uniform magnetic needle of strength of each pole is 98.1 amp, cm, is suspended from its centre by a thread. When a mass of 50 mg is loaded to its upper end, the needle becomes horizontal, then the vertical component of earth's magnetic induction is (g=981 cm//s^(2))
Answer» 0.50 gauss 0.25 gauss 0.05 gauss 0.005 gauss Solution : Taking MOMENT about O, `Mgl=mB_(V)L+mB_(v)L` `Mg=2mB_(v)` `(50)/(1000)xx981 = 2xx98.1xxB_(v)` `B_(v)=0.25` gauss