Posts Tagged ‘electricity’

In a corridor adjacent to the foyer of the Clarendon Laboratory at the University of Oxford in England, is an electric bell that has been ringing almost continuously since it was first displayed in 1840.

OxfordElectricBell1The Oxford Electric Bell, also called the Clarendon Dry Pile, was an experimental electric bell when it was first set up. It consists of two brass half-spheres or bells, each positioned beneath a dry pile battery, with a metal sphere, about 4mm in diameter, suspended between the piles, acting as a ‘clapper’. The sphere moves the very short distance between the bells by electrostatic force. As the sphere touches one bell, it is charged by the pile, is electrostatically repelled, and is attracted to the other bell. On touching the other bell, the process repeats itself.

Whilst a high voltage is required to create the motion, only a miniscule amount of charge is carried from one bell to the other, which is why the piles have been able to last since the apparatus was set up. 

OxfordElectricBell2It is not known for sure what the piles are made of – they may be Zamboni piles which are made of alternate layers of metal foil and paper coated with manganese dioxide – but they were coated with molten sulphur to insulate them and to reduce the effects of atmospheric moisture.

clarendon laboratory, oxford university, physics

The original Clarendon Laboratory in Oxford (photo taken in 1894) was the first purpose-built physics laboratory in the country. The building, much enlarged, is now incorporated into the Department of Earth Sciences.

The bell was apparently made by Watkin and Hill, instrument makers, of London, and purchased by the Rev Robert Walker, Reader in Experimental Philosophy (the name by which physics was known at Oxford) at the university from 1839 to 1860, and Professor of Physics from 1860 to 1865. It bears a label in his handwriting ‘Set up in 1840’.

The Oxford Electric Bell does not demonstrate perpetual motion as the bell will eventually stop when the dry piles are depleted of charge, if the clapper does not wear out first. It has now been ringing almost continuously for 175 years apart from occasional short interruptions caused by high humidity. A double-thick glass bell jar muffles the ringing sound, so the bell is inaudible. There is a video of the bell here.

The bell has rung about 10 billion times and is considered to be the longest running experiment ever. The Guinness Book of Records lists it as the ‘world’s most durable battery’.

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How do you decide what is the most featureless place? The Cambridge dictionary defines featureless as ‘looking the same in every part, usually in a way that most people consider to be boring’. Even the wildest parts of Scotland or the flattest fen in East Anglia have a ditch, bridleway, stream or hill to break the monotony.

Over ten years ago a listener to John Peel’s Home Truths show on Radio 4 asked about boring places in Britain. This triggered the search for Britain’s most boring place. The BBC turned to the Ordnance Survey to see if looking at maps would provide the answer on the basis that their large-scale maps show almost all features in the landscape. Maps are divided by grid lines into squares that are a kilometre wide and tall, and features are identified by various symbols. The obvious thing to do therefore was to find the grid square that had the least symbols in it. Was there a completely blank square among the 320,000 squares in the widely-used Landranger map series? This series of maps are at a scale of 1:50,000, that is one centimetre on the map is 50,000 centimetres on the ground, which is half a kilometre.

map, featureless, britain, ordnance survey, grid square, pylon, electricity, overhead line

This is how it looks on a map. The blue square in the middle has nothing in it except a single electricity pylon (the v-symbol) and the bit of overhead line between pylons.
© Ordnance Survey 2013

map, featureless, britain

The blue spot in the middle of this map, to the east (right) of Goole, marks the location of Britain’s most featureless place.
© Ordnance Survey 2013

After setting a computer to look at every one of the squares, the Ordnance Survey came up with answer! A field in the East Riding of Yorkshire is the most featureless place in Britain.

The square kilometre of farmland on the outskirts of the village of Ousefleet, just south of the River Ouse, near Scunthorpe, has nothing in it except a single electricity pylon and some overhanging cable. The square at grid reference SE 830 220 (the south-west corner of the square) on OS map 112 is as near as cartographers can get to a completely blank square in the Landranger map series.

featureless, britain, pylon, electricity, overhead line, ordnance survey, grid square, farmland

This is what the most featureless place looks like on the ground. The electricity pylon and the overhead line to the left lie just in the kilometre grid square, and that’s it. The rest is flat farmland.
© Roger Gilbertson/Creative Commons Licence.

Philip Round from the OS said at the time ‘We’re not saying it’s the dullest place in Britain. It might be the most fascinating place on earth but on our Landranger maps it has the least amount of information. No ditches, streams or buildings are shown on this particular scale of map. That’s quite some going, considering the low-lying areas of East Anglia and remote parts of Scotland.’

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The UK’s capacity to produce electricity is in the news. The energy regulator, Ofgem, has warned that spare capacity in power production could fall to 2% by 2015, increasing the risk of blackouts. The closure of ageing power stations, as well as tough emissions targets and the UK’s increasing dependency on gas imports, are all contributing to this heightened risk of shortages. But behind the scenes the matching of electricity supply to demand – electricity cannot be stored on a large-scale – remains a considerable challenge every day.

Most of our power is generated by fossil fuel power stations, which take half an hour or so to crank up to full power; nuclear power stations take much longer. If a cold spell is forecast there’s enough time to respond, and the same goes for the predictable increase in demand in the mornings and in the late afternoon. But when a popular TV programme finishes , many people go and put the kettle on, causing a sudden peak in demand for electricity that conventional power stations can’t meet instantly. How can electricity be produced immediately?

Pumped storage reservoirs are used to meet sudden peaks in electricity demand

Pumped Storage Reservoirs
To meet sudden peaks in demand for electricity, water is released from an upper reservoir to a low level reservoir on the way driving turbines and the generators that produce electricity. At night, the water is pumped back up to the top reservoir using cheaper electricity.

The solution is provided by pumped storage reservoirs. A pumped storage plant has two separate reservoirs, an upper and a lower one. When electricity is in low demand, usually at night, water is pumped into the upper reservoir. When there is a sudden demand for power, giant taps known as the headgates are opened allowing water from the upper reservoir to flow down through pipes to turbines which produce electricity, and back into the lower reservoir ready to be pumped back up later. To maximise the fall of the water, the four pumped storage plants are all in mountainous areas. The Cruachan and Foyers schemes are in Scotland, and Ffestiniog and Dinorwig are in North Wales. (more…)

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