The magnetic field at the centre of a circular coil of radius r carrying current I is B. What is the magnetic field at a point on its axis at distance r/2 from the centre?
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The magnetic field at the centre of a circular coil of radius r carrying current I is B. What is the magnetic field at a point on its axis at distance r/2 from the centre?

G1 Physics · Accepted Answer

On the loop axis, B(z)=B(0)[R²/(R²+z²)]^(3/2). At z=R/2, the factor is [1/(1+1/4)]^(3/2)=(4/5)^(3/2)=(2/√5)³. Hence C.