A2L Item 230

Goal: Applying the Biot-Savart law

Source: 283-645 Magnetic field from wire loop

The diagram shows a circular wire loop of radius R carrying current I.
What is the magnitude of the magnetic field, B, at the center of the
loop?

  1. 0
  2. μ0I/4πR
  3. μ0I/2πR
  4. μ0I/4R
  5. μ0I/2R
  6. None of the above.

Commentary:

Answer

(5) This question serves to identify students who do not know how to
apply the Biot-Savart law and/or those who are recalling the field due
to an infinite wire. This provides a good opportunity to discuss why
Ampere’s law is inappropriate for this case.