Dial Lamp Puzzle.

[Robert Darwent]

Of course! 50Hz AC is 3.14 x RMS Voltage yes? So half wave (zero voltage on the negative going half cycle) is half of 3.14 = 1.57.

After giving this a little more thought, you were almost correct David. If you'd put 3.14 x AVERAGE Voltage, you would have been spot on!

A sine wave varies between;

+/- 1 over 0.707 x its RMS value (with 1 over 0.707 = square root of 2)

or

+/- 1 over 0.636 x its AVERAGE value (with 1 over 0.636 = half of pi)

In my reply to Joe earlier, what I was telling him to do by multiplying his meter reading by 1.57 (1.5 to make it easier), is converting the AVERAGE value measured by his meter to the PEAK value;

1.11 (0.707 / 0.636 the form factor of a sine wave) x 1.414 (square root of 2) = 1.57 (half of pi)

Phew, talk about alternative ways of saying the same thing!

Hope this makes things a little clearer, but if it doesn't don't worry I've been confusing myself just as much before I got my head around it!

Regards