A circular loop of radius `R` carries current `I_2` in a clockwise direction as shown in figure. The centre of the loop is a distance `D` above a long, straight wire. What are the magnitude and direction of the current `I_1` in the wire if the magnetic field at the centre of loop is zero?

Answer

A, B, D

Explanation

`I_2` produces inwards magnetic field at centre.
Hence `I_1` should produce outward magnetic field.
or current should be towards right. Further,
`(mu_0I_2)/(2R) =((mu_0)/(2pi)) (I_1/D)`
`:. I_1=((piD)/R) I_2`