Re: [Phys-L] charge in an increasing magnetic field

[John Denker <jsd@av8n.com>]

It is not possible to create a magnetic field that is
uniform across all of space.  Therefore arguing about
whether such a thing has a "center" is like arguing
about the color of unicorns.

Secondly, the original question had nothing to do with
a field that is uniform across all of space.  Do we
really need to argue about the color of /off-topic/
unicorns?

On 04/15/2015 09:23 AM, Philip Keller wrote:

> A region of space is filled with a uniform magnetic field, directed in the
> z-direction, increasing linearly with time, with the "center of the field
> at the origin.

That is a 100% reasonable question.  It is not necessary
or in any way advantageous to nitpick the question.

The question may contain more details than are strictly
necessary ... but the details are mutually consistent.
This situation is 100% typical of real-world questions.

  In contrast, for those who are accustomed to seeing
  only end-of-chapter questions where the information
  is exactly necessary-and-sufficient to find the answer,
  that's your problem.  Please don't inflict your
  problem on other folks.

  I am quite aware that within the PER community there
  is a school of thought that advocates giving students
  just barely enough information, so as (in their words)
  to "compel" students to solve the problem a certain
  way.  However, this is always unwise and sometimes
  disastrous, as in the example discussed here:
      https://www.av8n.com/physics/heller-third-law.htm


FURTHERMORE, even if the original question had been open
to multiple interpretations, it would be polite to
interpret in the way that makes the most sense.

People actually built and operated a number of betatrons
in the 1940s and 50s, so it is entirely reasonable to
ask about such things.