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It doesn't matter what they (SI) did - that's the point. The concept of energy is independent to the concept of time. You can express it in terms of a different quantity (such as Watts) and time (i.e. watts times time) and simultaneously introduce a new time unit on the numerator and...

SI could have chosen to define the Joule in terms of the amount of energy required to increase the temperature of X Kg of a substance (water?) by Y Kelvin. Both Kelvin and Kg are SI base units. There's no need for energy to be defined in terms of time; it's done that way for convenience...

My interpretation of securespark's last post was that some combinations of LEDs with differing / mismatched Vf values light when put in parallel and some other combinations do not. I believe this is because the LEDs in question won't have the "ideal" brick wall V/I characteristic - a real...

I expect that's due to the voltage current characteristics for the specific LEDs. An "ideal" diode doesn't pass any current until its Vf is exceeded at which point it starts conducting. When conducting, it always drops Vf volts across it regardless of the current. That's just an idealised...

If the sum of the forward voltages of the LEDs is close to the total cell voltage that may be fine but you would probably be exceeding the LEDs' rated current. Depending on the difference, this may or may not be OK. If the difference is too great, the LEDs may fail and the battery and LEDs...

Semiconductors including LEDs have a relatively fixed voltage drop across them when conducting - called Vf in the case of an LED. The LEDs you have will have different Vf values but, by connecting the anodes and cathodes together, you have ensured that both anodes are at the same potential...

Thanks guys - I suspected as much but you never know what tricks other people may have thought of. I have some interesting electronic test kit but no TDR unfortunately,

I don't think I explained myself very well. By directly-connected, I meant sockets which are immediately next to each other on the spur (i.e. there are no other sockets in-between). To incorporate the end socket into the ring on a guaranteed single-socket spur I'd need to identify the socket...

What I should have said is that I had some more work to do - I'm in absolute agreement with you on the need for a systematic approach and I'm grateful for your help! Over the last couple of days: I've re-checked all other sockets in the house and this is the only socket which could be the...

A minor breakthrough perhaps. I've found a 'red' socket that has a single cable to it. So, it seems this may be the end of the unfused spur. The dumbbell idea seems unlikely now and was only a theory - an attempt to explain where the end of the unfused spur might be to in a manner that fitted...

I've checked the sockets in question and they have two wires going to them so I can't find the end of the unfused spur. I'd hazard a guess that the builder thought he had extended the ring (hence he ran two new cables from the same room to the extension) but got it wrong. Maybe there's JB...

Yes - there are two cables (both 2.5mm2 T&E) which come from the CU and go under bed 2. The complete ring seems to supply bedrooms 1, 3 and one socket in bed 2. The remainder of the sockets in bed 2 and those in bed 4 appear to be fed from the radial type lashup off the ring. As you say...

Will do and thanks for the advice. We'll be doing IR testing when my electrician friend comes over as I don't own the gear.

Well, I decided to try and narrow things down a little by lifting some accessible floorboards in the hallway which is currently uncarpeted. This gave me access to the cables of the RF circuit as it goes between rooms. I checked for voltage on the cables with a megger pen before and after...

The isolator is located in the cutout before the meter so some good news at last. My original intention was only to paint a room and replace the skirting. The DMM is a tektronix TX-3 performance for the 50 ohm range, 5,000 counts: resolution 0.01 ohm, accuracy ±(0.1% + 10 counts). Sounds...

There's a double pole isolator which I'd presumed to be sufficient although I guess it does leave CPC connected back to neutral at the substation or service head. I'm aware the MCBs are single pole so only isolate L. I've been testing between like conductors (i.e. L to L, N to N etc.). It's...

Hi all I'm renovating a room in our house and came across a badly installed socket with a blackened wire running next to a CH pipe in a notch between floorboards. This socket was spurred off the ring final using bare terminal blocks. We have two 32 A RF circuits - one for kitchen and one for...

I'm replacing my halogen GU10s with LEDs. LED GU10s can be expensive and many of the cheap ones don't produce enough light. The best one I've found so far is the "Philips master 7w" at £18 each. I prefer the light to 50w halogen GU10s and they're about the same brightness. Compact...

Could you vent it to a soffit board instead?

How about this? http://www.screwfix.com/p/no-nonsense-instant-plaster-filler-310ml/72591?_requestid=888777