I amount of current is passed through a coil with N turns. Magnetic flux linked with the coil is ......

Explanation

1. Magnetic force on CD should be balance with weight force.
2. Resultant torque should be zero for equilibrium.
3. Torque = moment of force
`tau` = (Force) (perpendicular distance from reference point)
4. In the absence of magnetic field,
Torque on one arm = torque on second arm,
`thereforemg(l)=W_("Coil")l`
(Where l = distance of mid point from any one end)
`therefore(500)gl=W_("Coil")l`
`thereforeW_("Coil")=(500)(9.8)N`
5. In the presence of magnetic field : Suppose in presence of magnetic field mass m is adding in mass M. For this situation,
`(Mg)l+(mg)l=(W_("Coil"))l+(IlBsin90^(@))l`
but `Mgl=(W_("Coil"))l`
`thereforemgl=(ILB)l" "("where "L="length of CD wire")`
`thereforem=(BIl)/g=(0.2xx4.9xx10^(-2))/9.8`
`thereforem=10^(-3)kg`
m = 1 g