Two short magnets of magnetic moments 0.135 and `0.255 A - m^(2)` are kept with their axes perpendcualr to each as show in the adject figure . The distances of the magnets from the points of intersection are 30 and 40 cm respectively. The resultant magnetic field a the point of intersection will be .

Options

A. `2.56 xx 10^(-6) Wb//m^(2)`
B. `2.56 xx 10^(-7) Wb//m^(2)`
C. `1.28 xx 10^(-6) Wb//m^(2)`
D. `1.28 xx 10^(-7) Wb// m^(2)`

Answer

C

Explanation

`B_(1) = (mu_(0))/(4pi ) (2M_(1))/(d_(1)^(3)) = (10^(-7) xx 2xx 0.135)/((0.3)^(3)) = 10 xx 10^(-7) Wb// m^(2)`
`B_(2) = (mu_(0))/(4pi) (2M_(2))/(d_(2)^(3)) = (10^(-7) xx 2xx0.256 )/((0.4)^(3)) = 8 xx 10^(-7) Wb//m^(2)`
`therefore B = sqrt(B_(1)^(2) + B_(2)^(2)) = sqrt(100 + 64) xx 10^(-7) Wb//m^(-2)`