Two short bar magnets of length `1cm` each have magnetic moments `1.20 Am^(2) and 1.00 Am^(2)` respectively. They are placed on a horizontal table parallel to each other with their `N` poles pointing towards the south. They have a common magnetic equator and are separted by a distance of `20.0 cm`. The value of the resultant horizontal magnetic induction at the mid - point `O` of the line joining their centres is close to (Horizontal component of earths magnetic induction is `3.6 xx 10.5 Wh//m^(2)`

Options

A. `3.50 xx 10^(-4) Wb//m2`
B. `5.80 xx 10^(-4) Wb//m2`
C. `3.6 xx 10^(-4) Wb//m2`
D. `2.56 xx 10^(-4) Wb//m2`

Answer

4

Explanation

`B =B_(1) + B_(2) + B_(2) = (M_(0))/(4pi) [(M)/(R )^(3) + (M)/(r)^(2))]+B`
` 10^(-7) [(1.2 +1)/(0.1)^(3)] +3 3.6 xx 10^(-5)`
` = 2.2 xx 10^(-4) + 3.6 xx 10^(-5)`
` =2.56 xx 10^(-4)` .