OBSERVATIONS    GM1SXX             17th NOV 2009A

Hertz & Cycles per Second

(See LINK for more background)

For anyone new to this thread, I had to mark a student wrong in a Foundation exam question a few months ago that asked...

Here is my response to the Exams Committee. All of the names involved have been  obscured.

73 Al.

GM1SXX

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NOTE, because of this...

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I can't reproduce the entire reply from RSGB, I can only post my own replies to them.

73 Al.

GM1SXX

This is today's reply to the Exams Committee

Hi XXXXX,

Could you please pass this email on to XXXX XXXXX for me.   It took me a few seconds  to look this up.  Unfortunately I type very  slowly.

XXXX said..

>Hertz and c/s.  The answer to your point is actually quite simple and indicates the need for some precision of expression.

The UNIT of frequency is the Hertz, cycles per second is a description of what that is, but it is not defined as the unit.  It is not expected that we will hold that philosophical discussion with the candidates unless they ask, but we should take care to be correct in our use of terminology. I don’t follow your argument about realising they have been ‘had’ at the higher levels.  The fact that the description is the number of cycles in one second should be covered at Foundation level at the same time.  Describe what it is and define the unit of measurement.

From Wikipedia, the free encyclopedia

The cycle per second was a once-common unit of frequency.

and Hertz…. Also from Wikipedia

The hertz (symbol: Hz) is a unit of frequency. It is defined as the number of complete cycles per second. It is the basic unit of frequency in the International System of Units (SI), and is used worldwide in both general-purpose and scientific contexts. Hertz can be used to measure any periodic event; the most common uses for hertz are to describe radio and audio frequencies, more or less sinusoidal contexts in which case a frequency of 1 Hz is equal to one cycle per second.

Re the question I posed,   I wasn’t quoting the syllabus contents,  but instead the content of an  actual exam paper where two of the possible answers presented were ‘Hertz’ and ‘Cycles per second’.  How does It is a basic tenet of teaching that one does not say something which has to be denied later, but which can be presented as less than the whole story and which is now expanded into further detail… sit with this, when both units do have the same meaning?    

Syllabus apart. Cycles per second may be an  obsolescent  term, but as you’ll probably  be aware, Megahertz and Megacycles are used interchangeably in the real world along with Kilohertz/Kilocycles and Hertz/Cycle per second by many older people.  OK we  ‘old codgers’ will eventually die out , SI will reign supreme and Hertz will become the universally used  unit, but it’ll be a while yet.