(Solved): (a) In the lecture notes, you find how the magnetic field of a toroid is determined. Please explai ...

(a) In the lecture notes, you find how the magnetic field of a toroid is determined. Please explain in your own words (but please restrict to one page only), how the magnetic field of a toroid can be calculated. (b) You have a toroid with circular cross-section with inner diameter a of \( 1 \mathrm{~m} \) and an outer diameter \( \mathrm{b} \) of \( 2 \mathrm{~m} \). A wire is wrapped around the toroid with 10000 turns. A current of \( 10 \mathrm{~A} \) is running through the wire (see picture on the right). Determine the magnetic field at \( \mathrm{r} \) (in the middle between a and \( b \) ).