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[Yorkie]

My head still hurts and now going for two Anadin and a mince pie, but not necessarily in that order.

[sevenlayermuddle]

My head still hurts and now going for two Anadin and a mince pie, but not necessarily in that order.

I don't blame you.  In my case I've reached for the beer, but I daresay the mince pie will follow if one can be found, and an Anadin tomorrow morning would probably be very welcome.  As for all these equations, I don't even remember who started it.

[guest]

The problem is really that the transmission lines carry AC (alternating current) rather than DC (direct current). This causes rather hideous problems with anything other than a pure resistive load - which in the real world of electricity distribution doesn't exist - the cables themselves have inductance and there's a capacitive effect to ground via the air.

Basically when you have an inductive (or capacitive) load then the current and voltage aren't in phase which can cause significant problems if they're not adequately managed - like hotspots so severe in the transmission cables that they melt.

High voltage DC (HVDC) interconnectors are used to connect the power stations to the national grid but they are mind-bogglingly expensive. They are low-loss though as you can imagine as there's no AC involved.

Edit - there's a reason you see birds sitting on the big pylons/cables. The cables are warm to the touch in places

[scottiesmum]

Yorkie,  For goodness sake don't tell your local council your pylon is humming  ....   they'll  surely charge you 

[sevenlayermuddle]

The problem is really that the transmission lines carry AC (alternating current) rather than DC (direct current). This causes rather hideous problems with anything other than a pure resistive load - which in the real world of electricity distribution doesn't exist - the cables themselves have inductance and there's a capacitive effect to ground via the air.

Basically when you have an inductive (or capacitive) load then the current and voltage aren't in phase which can cause significant problems if they're not adequately managed - like hotspots so severe in the transmission cables that they melt.

High voltage DC (HVDC) interconnectors are used to connect the power stations to the national grid but they are mind-bogglingly expensive. They are low-loss though as you can imagine as there's no

Rizla,

Thanks for that.  There's two reasons I didn't mention AC vs DC...

1) (The excuse:) It's harder to explain, and I wanted to keep it simple.
2) (The truth:) The days when I understood it to the point of being able to comment constructively are long gone.

Thanks for the interesting clarification,
7LM

[tonyappuk]

I can still hear my old physics teacher telling us, "Rest = Coffin Under Earth" or Resistance = Current under EMF or Volts. It's amazing what sticks in the mind.
Tony

[dave.m]

Tony,

Showing my age but I can still remember:

Tommy On A Ship Of His Caught A Herring.

Tangent, Sine and cosine regarding angles and length of sides of triangles.

Always remember saying, "Wonder what they did before Log Tables."    

And slide rules. Still got two of mine.
dave

[tonyappuk]

Mine was SOHCAHTOA which I found rememberable and my slide rule is still in my tattered old briefcase under the desk. We are becoming maudlin, Dave. Time for bed.
Tony

[guest]

Here's a novel idea to save power - use AdblockPlus & NoScript to kill flash adverts. It will apparently save you enough power to run an 11W low energy lightbulb - http://www.theregister.co.uk/2008/12/02/green_browsing_study/

Personally I've done it for ages but simply because I hate adverts. Flash adverts are definitely the spawn of satan though, regardless of your feelings about saving energy/green stuff 

[oldfogy]

My original formulae on page 2 contained an error (and has also been corrected).
Here is the correct "and" additional formulae.

********************
V = Volts, A = Amps, R = Resistance (ohms) W = Watts
Providing you know any 2 of the above values, it is then possible to find the value of any other value.

  V ................ W
----- ............ -----
A x R ........... V x A

Use either formulae to find:

Volts = Amps x Resistance
Volts = Watts divided by Amps

Amps = Volts divided by Resistance
Amps = Watts divided by Volts

Resistance = Volts divided by Amps
Watts = Volts x Amps

****************
edit:
Correction and addition to formula's