1. The problem statement, all variables and given/known data I have attached a diagram with the question. 2. Relevant equations Biot-Savart law: (μ/4π)(I/r^2)(dlxr) or (μ/4π)(q/r^2)(dvxr) 3. The attempt at a solution My question is, The B field can be predicted from the right hand corkscrew rule right? So the part of the rod that exerts a B field on point P is only the small portion of the rod at the origin right? The answer key shows some intergral over the whole length of the rod which I do not understand as I think the part of the rod that creates a B field at point P is only the little bit at the origin. Thanks.