I probably should have said “examples”, as the cases that I am most familiar with are from the last half of the 20th century.
Maybe a historian can comment on restrictive European and American trade practices, other than high tariffs, in the 19th century.
The DIN connectors for audio vs RCA jacks used in the USA and Japan, and the French SCART A/V connector, which by law all tv’s sold in France must have
The elephant that Edison electrocuted publicly in one of the demonstrations was rather famous at the time. Edison’s film of the event is linked also (warning: disturbing!)
For the record, Cecil has also talked about this: How come the U.S. uses 120 volt electricity, not 240 like the rest of the world?, although I think there’s nothing in that article that hasn’t already been said in this thread.
Arjuna34
Until I read the circumstances surrounding the electrocution, I was giving it a :dubious: thought. Although I could imagine Edison pacing up and down his living room the day before thinking “nice plan, if only I could get hold of an elephant…”
And I also know that the power supplied to houses in Poland is much the same as that in the UK, despite the difference in shapes of electricity sockets. I know this because my Polish housemate plugged her two pin plug into a three pin socket in our kitchen. When I asked her how she got the supply to work she happily described sticking a knife into the top socket to get the power flowing…
Re-read my request. I very much doubt these date from before 1920!
The top socket is only the earth connection , so in theory she won’t come to any harm. But knowing it might have been wired up by a cowboy electrician, I would not have risked it.
What’s described here is actually a common, known hack to hook up a Euro plug into a BS 1363 outlet. The pins are compatible, but a way have to be found to overcome the interlock which blocks both hot and earth slots (which are unlocked by inserting the ground pin into the outlet, which by the British standard is longer than the other two).
Your friend could have also bought a BS1363 to Europlug adapter, which are commonly available and have a 5 or 10 AM fuse for protection. Otherwise she risks having 30 A of current pass through a cable designed for maybe 2-5, before the circuit breaker trips
It certainly has been done [eg. http://www.nictd.com/links/ourhistory.htm ].
It was the invention of the transformer thaat gave AC the leg up. You could transfer electricity at high voltages (therefore with low current) over great distances, resulting in low voltage loss over such distances and then convert voltage signature back into current signature where it is actually used. There is no such analogous technology for direct current.
For DC, Heat dissipation within the wire itself (for std high-tension powerlines) might be a factor of 1000x more than AC - causing energy loss and potential fire hazard. Efficiency (AC) won in the many battle for resources later on. In fact, at great distances using DC, you might find it hard getting any voltage difference (across leads) at all.
Transformers were well known(at least in the laboritories) prior to Edison’s involvement. What there was NOT were good AC motors. It was Nikola Tesla’s invention of the AC induction motor that was the death of DC. Even then, motors that needed high torque over a wide speed range needed to be DC, hence the elevators mentioned earlier in this thread. Nowadays solid state inverter drives can supply induction motors with variable frequency power, allowing them to mimic the performance of the old DC motors with out the brushes to maintain.
For a real mess regarding electricity, you want to take a look at the electrified railways of Europe. Virtually every country has a different system . It can be either AC or DC and the voltage can vary from 750 volts up to 25kV. Even the frequency can vary. Some countries uses 16 2/3Hz and other 50 Hz. This means that to use the same locomotive for cross-border traffic it has to be equipped with multiple systems. In Europe, it is common to use four-system locomotives (DC 1.5 kV, DC 3 kV, AC 15 kV 16-2/3 Hz, AC 25 kV 50 Hz).
To complicate matters you have both the overhead and third rail current collection systems. Eurostar trains through the Channel Tunnel are multi system because a significant part of the route near London is over the old UK 750 volt ‘third rail’ system. The French part of the journey is 25kV AC , and the route into Brussels is electrified at 3000 V DC . These latter two use overhead collection.
I remember reading that train speeds over the old UK lines were limited because the DC rails could not supply all the power that the trains were capable of handling. I believe the new line into London is being built to French (25-kV) standards.
That is correct. The first part of the new line is already open, with the rest following in a couple of years. BTW, 25 kV is not just a “French” system . The vast majority of the UK electrified railway north of the Thames already uses 25kV AC with overhead collection.
I have just found this list which shows railway electrical systems world-wide.
Running Eurostars over the suburban third-rail network was really always a compromise. The speed restrictions weren’t just because of the power supply, but because it simply wasn’t a high-speed network.
Am I right in thinking that as well as the third-rail overland system, the London Underground also works off DC?
Correct . According to the above list it’s 630 volts DC , using a four-rail system as opposed to the three-rail system of the main-line railway. I think the difference between these two systems is that the third-rail network uses a running rail as one of the conductors, whereas the underground has separate rails for the is function