Question

please tell me why the explanation up-to R (first half of the graph) ​

Answer 1

Explanation: The formula for the magnetic field due to a current carrying conductor within the radius :-

B=[(μ0) ×(I) ×(x) ] ÷[2π(R^2) ]

Here except x, all others are constants, so, from x=0 to x=R, where R is the radius, the magnitude of the magnetic field keeps increasing linearly (straight line) , and when x=R, the magnitude attains the maximum value, and after that, it starts decreasing , but the decreases is somewhat faster than gradual and so attains a negative curved slope after the point of radius R!