# 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?

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. WhileIandpare limited to one digit, no limit is given forn.The only sensible thing to do is therefor to pick

Iandpas the free variables and test if a correspondingnexists.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..