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Sunday Times Teaser 2954 – Lovely Meter, RITA Made!

by Stephen Hogg

Published May 5 2019 (link)

Revisiting the old curiosity shop, I bought an unusual moving-iron ammeter (made by Rho Iota Tau Associates). On the non-linear scale “9” was the last possible “whole amperes” scale graduation marked before the “full scale deflection” end stop (which was a half turn of the pointer from zero).

The booklet gave the pointer swing from zero (in degrees) equal to the current (in amperes) raised to a fixed single-figure positive whole number power, then divided by a positive whole number constant. Curiously, the angle between “exact” pointer swings, calculated using this formula, for two single-figure “whole amperes” values was exactly a right angle.

What, in amperes, were these two currents (lower first) and to what power were they raised?

4 Comments Leave one →
  1. Brian Gladman permalink

  2. Erling Torkildsen permalink

    • Erling Torkildsen permalink

      A critical comment on my Python-program above.
      The angles in question are given by the three variables: the current (I), and a ‘calibrating’ exponent (p) and divisor (n), all integers. While I and p are limited to one digit, no limit is given for n.
      The only sensible thing to do is therefor to pick I and p as the free variables and test if a corresponding n exists.
      My programme (above) fails to do that. It was written spontaneously and gave a solution directly, that flattered the author and weakened his critical sense..

  3. GeoffR permalink

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