A symmetric star shaped conducting wire loop is carrying a steady state current I as shown in the figure.…

A symmetric star shaped conducting wire loop is carrying a steady state current I as shown in the figure. The distance between the diametrically opposite vertices of the star is 4a. The magnitude of the magnetic field at the center of the loop is

  1. μ0I4πa 3 3-1
  2. μ0I4πa63-1
  3. μ0I4πa6 3+1
  4. μ0I4πa32-3

Solution

The given points (1, 2, 3, 4, 5, 6) makes 360o angle at ‘O’. Hence angle made by vertices 1 and 2 with ‘O’ is 60o.

Direction of magnetic field at ‘O’ due to each segment is same. Since it is symmetric star shape, magnitude will also be same.

Magnetic field due to section BC.

B1=kia sin60°-sin30°=ki2a 3-1

Bnet=12×B1=6kia 3-1 and k=μ04π

Asked in: JEE Advanced 2017 (Paper 2)

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