Q.

As shown in the figure, a long straight conductor with a semicircular arc of radius π10m is carrying current I=3 A. The magnitude of the magnetic field at the center O of the arc is (The permeability of the vacuum =4π×10-7 NA-2).           [2023]

1 6μT  
2 1μT  
3 4μT  
4 3μT  

Ans.

(4)

BC=μ0I4πR(π)  (B at centre of circular arc)

=μ0I4R=4π×10-7×34×π10=3×10-6 T=3μT