**Goal:** Reason regarding the fields due to current elements

**Source:** 283-650 Maximum B field

In all cases the wire shown carries a current I. For which situation

is the magnitude of the magnetic field maximum at the point P?

**Goal:** Reason regarding the fields due to current elements

**Source:** 283-650 Maximum B field

is the magnitude of the magnetic field maximum at the point P?

## Commentary:

## Answer

(4) #4 is larger than #3 because contributions from the two half circles

reinforce in #4 rather than oppose each other as in #3. #4 is larger

than #1 because #4 has a half loop at half the radius. Situation #2

having a finite length of wire is a distracter. The field in #2 is

smaller than #3 and would be even if the wire in #2 were infinite. An

interesting follow-up is to ask students to well order the cases

according to the strength of the field.