Question

# A solid cylindrical conductor of radius R1 is kept inside a hollow cylindrical conductor of inner radius R2 and outer radius R3(R1<R2<R3) in a co - axial manner, as shown. The solid cylinder carries a current I1 and the hollow conductor carries current I2 in the opposite directions. The two conductors are kept insulated from each other and current through each is distributed uniformly over the cross–section. Let r be any radial distance from the axis. Magnitude of magnetic induction B at points outside the solid conductor such that R1<r<R2 will be

A
μ0(I1+I2)2πr
B
μ0(I1I2)2πr
C
μ0I12πR21r2
D
μ0I12πr

Solution

## The correct option is D μ0I12πrConsidering amperian loop (2) ∮→B.→dl=μ0 iencB(2πr)=μ0I1B=μ0I12πr

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