Question

A wire carrying current i has the configuration shown in figure. For the magnetic field to be zero at the centre of the circle, θ must be:

Options

• 1 radian

• 2 radian

• π radian

• 2π radian

Answer 1

2 radian

Explanation:

Refer to figure given in question

For magnetic field at centre to be zero

`(mu_0"Id"l)/(4pi"R"^2) = (mu_0"I")/(4pi"R")+ (mu_0"I")/(4pi"R")`

∵ dl = Rθ

`(mu_0"IR"theta)/(4pi"R"^2) = (mu_0"I")/(4pi)[1/"R"+1/"R"]`

or θ = 2 radian