I love this forum.

[nigelwright7557]

Some people seem to think they can fix things with zero knowledge.
A prod here or a poke there.
I have been doing it for 40 years and still don't know it all by any stretch.
The thought that these people are poking around inside amps with mains is a but frightening.

I remember doing my city and guilds in electronics in 1980 and I had a bit of spare time so asked my tutor if I could build a valve pre amp for my guitar.
He said it was fine so I built it up and it didn't work.
So in my infinite wisdom I touched the circuit and got a huge belt.
The tutor said to discharge the capacitor before touching it.
Ok fair enough.
So I powered it up again and it still didn't work.
So I discharged the capacitor and touched the circuit and got a huge belt again !
I had forgotten to turn it off, DOH !

Its amazing I ever reached 61 but I have been much more careful since the valve pre amp days. On my valve circuits I now always include a LED + resistor across B+ to show when its charged or live.

 

[Bigun]

I have been doing it for 40 years and still don't know it all

Don’t worry, many of us do in fact know it all

 

[scottjoplin]

Somewhere I read recently someone had made a distinction between FAST and FAW (fullrange and woofer) obviously they had missed the point

**** Nigel! I'm scared

 

[nigelwright7557]

Don’t worry, many of us do in fact know it all

Until the next question !

I work as a GCSE maths tutor part time.
I just think I get to the point where I can answer everything and then a new exam question gets me.
I am told I am brave as I tend to just work through old exam papers with students. This means I don't know what is going to come up next.
A lot of tutors just use lessons they have pre-made up themselves so there is little chance of being caught out with a question.
MY A level and GCSE is 20 years old and the examiners keep on adding in new stuff that I haven't done before. A lot of stuff has come down from A level to GCSE level too.

There is a Fibonacci sequence where current number is sum of two previous numbers. A is first number and B is third number work out the fifth number in terms of A and B.

So we have A X B C D
So X = B-A
B=A+X
C=X+B
D=C+B
Therefore:
B=A+B-A
C=A+B-A +B-A
D=A+B-A+B-A +A+B-A
Answer = 3B-A

Once you realise what to do it is very simple, just substitution.

 

[scottjoplin]

I remember I passed a chemistry test by adding up the numbers after the letters, kinda lost faith after that

 

[nigelwright7557]

I remember I passed a chemistry test by adding up the numbers after the letters, kinda lost faith after that

I had a question throw one of my younger students.

What is square root of 9 squared minus square root of 7 squared.
Square root of anything squared is just that number
So answer is 9-7=2 don't even need a calculator.

 

[Galu]

I only ever passed my maths exams at the final permitted attempt.

Of course that was back in the days of log tables and slide rules!

 

[Charles Darwin]

Any maths that go beyond the simple calculator functions get passed over to my daughter

 

[MAAC0]

Speaking of square roots, what's the Square root of -1 ?... It's called "i" and now we are in the world of imaginary numbers...

 

[scottjoplin]

Those are very useful for calculating the size of polypropylene caps in parallel with PSU smoothing caps.

 

[Galu]

Originally posted by scottjoplin >
I remember I passed a chemistry test by adding up the numbers after the letters.

That, of course, is exactly how you check that a chemical equation is balanced e.g. CuCO3 + H2SO4 = CuSO4 + H2O + CO2

So you're really a clever boy after all!

 

[Galu]

It's called "i" and now we are in the world of imaginary numbers...

My imaginary number is called 'Arthur'!

 

[nigelwright7557]

Speaking of square roots, what's the Square root of -1 ?... It's called "i" and now we are in the world of imaginary numbers...

The world where sqroot(-1) * sqroot(-1) = -1
And the world of conjugates.

 

[tsmith1315]

My imaginary number is called 'Arthur'!

Mine is eleventeen, courtesy of Bill Watterson.

 

[Galu]

Had to look that up Tim - not so familiar with the Calvin & Hobbes comic strip on this side of the pond!

 

[tsmith1315]