The discussion revolves around calculating the magnetic field produced by a semi-infinite wire. Participants are attempting to apply the relevant equation, B = μi / 4πR, but are uncertain about how to determine the appropriate value for R in different scenarios presented in the problem.
Some participants have provided guidance on understanding the conditions under which the formula applies, emphasizing the importance of the geometry of the problem. There is an ongoing exploration of how to interpret the problem's requirements and the implications of the assumptions made.
There is a noted ambiguity regarding the locations of the points where the magnetic field is to be calculated, as well as the specific conditions under which the formula for the semi-infinite wire is valid. Participants are also considering the relevance of currents within certain radii in relation to the magnetic field calculations.
The text at that link does answer your question. In brief, it is only the currents inside the selected radius r that matter. For r<b, what is the current inside?Adeel Ahmad said: