Reverend Nicholas Callan and the Induction Coil

Rev. Nicholas Callan. Public domain image via Wikimedia Commons: https://en.wikipedia.org/wiki/Nicholas_Callan...

Did you know that the induction coil is an Irish invention by Reverend Nicholas Callan (1799 - 1864), a physicist and Catholic priest at Maynooth University?

The device is a type of transformer, commonly used in vehicles in the form of an ignition coil for generating the tens of thousands of volts necessary to create a spark at the plugs. Induction coils with an output of hundreds of thousands of volts were used for early spark-gap transmitters. Connected to a tuned circuit and antenna, they could transmit radio waves at a certain frequency. The tuned circuit is the electrical analog of a bell. A spark discharge "rang" the bell by setting off electrical oscillations.. These transmitters would have been used for intercontinental and ship-to-shore communications in the era of the Titanic.

 

Electromagnetic Induction 

 

Electromagnetic induction is a phenomenon discovered by the English scientist Michael Faraday in 1831. If you move a magnet close to an electrical conductor, e.g. a looped piece of wire, the field of the magnet induces an electric current in the wire. It's the change in magnitude of the magnetic field that creates the current, rather than the fact that the magnet is moving. If the field is constant in magnitude, no current is induced. The magnitude of the voltage that creates the current is proportional to the rate of change of magnetic flux, in other words, the faster the magnetic field changes in size, the greater the voltage.

 

How Do Transformers Work?

 

All transformers and electrical generators work on the principle of electromagnetic induction.

The transformers such as those used in older power adapters and corded electronic equipment have a laminated core, made of a stack of wafer-thin, soft iron sections, insulated from each other. A primary coil wound around the core (hundreds of turns of wire) generates a fluctuating current when connected to an AC mains source. This in turn creates a fluctuating magnetic field and that field then induces an electric current in a secondary winding. A transformer simply increases voltage, or decreases it, like the room sized transformers we have at the sub-station in Kilcullen. The ratio of the number of turns of wire on the primary coil to those on the secondary coil, known as the turns ratio, determines the factor by which the output is increased or decreased. So if the input coil has 1000 turns and the secondary coil has 100 turns, that's a turns ratio of 10 and voltage is reduced by a factor of 10

 

Schematic of a transformer. Image author BillC at the English-language Wikipedia, CC BY-SA 3.0

 

What are Induction Coils?

 

Instead of being fed by AC, an induction coil works on DC. It has a primary coil with hundreds of turns of wire and a secondary with thousands of turns. The coil when energised also acts like an electromagnet. This isn't the case with a standard transformer because the iron core is in the form of a closed loop, with no external field. The DC source, e.g. a battery, is connected to the coil via a spring switch, called an interrupter, that can be opened and closed by the force of the electromagnet (the same mechanism is used on old doorbells). On connection of the supply, with the switch closed, the magnetic field in the core grows until the electromagnet suddenly opens the switch, disconnecting the input. The magnetic field rapidly collapses and it's this rapid collapse and change in field that induces a huge voltage in the secondary, much greater than the turns ratio could produce with an AC source. When current is disconnected by the switch, the force of the electromagnet drops to zero, causing the spring to close the switch again, reconnecting the circuit and the cycle repeats indefinitely, generating high voltage pulses at the rate of hundreds per second.

 

An induction coil. Image courtesy Hannes Grobe, CC BY 3.0 via Wikimedia Commons

 

More information on Rev. Nicholas Callan on the Maynooth University website here:

https://www.maynoothuniversity.ie/electronic-engineering/callan

#scienceweek #ScienceWeek2024

Kildare DC Electric Station

Image courtesy Brian Murphy, KILDARE DC ELECTRICITY STATION, Cill Dara Historical Society: Kildare Town Heritage Series No. 37 (https://www.facebook.com/kildaretownfootprints/posts/147252716928373) - Accessed 16/10/24

 

Nowadays we use natural gas in our homes and industry. It comes from natural gas deposits such as the offshore Corrib gas field off the coast of Mayo and previously from the Kinsale Head gas field which is now depleted. We also import gas from the UK and mainland Europe through several gas interconnectors. Natural gas is pretty much odourless methane, with an odoriser added for safety reasons.

 

Coal gas

 

Before the advent of natural gas, cities and many towns had their own gasworks. Coal was roasted to create a gas which could be stored in large tanks called gasometers and coke and tar remained as by-products. Tar could be used for road building and coke used as a fuel domestically or in foundries for smelting iron ore.

 

The Kildare DC Electricity Station

 

In the Kildare station, just like in a gasworks, gas was produced from coal in a gas plant room. The article doesn't mention how the liquid fuel was obtained, but presumably the gas that was created from roasted coal was distilled and condensed to a liquid that could be stored and used to power the engines. This process known as gasification isn't limited to coal as a raw product. In fact any biomass can be used that contains cellulose, such as wood chip. During WW2 when there were fuel shortages, modified "wood gas cars" and buses ran on such fuels, with an onboard or towed gasifier generating the fuel gas.

 

This article about the Kildare DC Station by Brian Murphy was first published in the Kildare Nationalist in 2009.

Automatic Telephone Exchanges

A panel of stepping switches at a telephone exchange. Public domain image via Wikimedia Commons.

 

In Ireland, unlike the UK, we skipped having transistorised telephone exchanges and went straight from electromechanical (using relays, coils and motors) step-by-step or more modern crossbar systems to digital versions. When I was in the boy scouts in the 70s, I remember the whirring and clicking coming from the small telephone exchange building adjacent to our den (located in the tennis club building), as the exchange switched calls. Electrical pulses from a subscriber's telephone (known as pulse dialling, now replaced by tone dialling) caused a shaft on one of the mechanisms in the exchange to turn by a varying angle, the angle depending on the number of pulses. Each number from 0 to 9 on the dial of a telephone handset generated a different number of pulses. The shafts on the mechanisms in the exchange had an arm or arms attached, with electrical contacts on the end of the arm. As the arm swept around (usually limited to a half circle), it made contact with another set of stationary contacts, the process enabling a call to be connected to another number locally. Trunk calls to another "area code" would be sent to the exchange in Naas to be distributed to other local exchanges. From what I recall, in the early 70s, either Byrne's supermarket in Kilcullen or Athy still had a handset without a rotary dial, sitting near the meat counter at the back of the shop, presumably dating back to before the days of the automatic exchange.

 

This is an RTE report from 1989 about the changeover.

https://www.rte.ie/.../1045651-last-step-by-step.../

How Kilcullen Gets Its Power and Poulaphouca Dam

Construction of the Poulaphouca Dam. Image courtesy O'Dea Photograph Collection, The National Library of Ireland. Photographer James O'Dea

The Liffey Reservoir Bill was signed into law and became an act in 1936. Construction of the dam commenced in 1937 with flooding of the Liffey Valley beginning in 1940. The hydroelectric power station was finally commissioned in 1947.

How Does the Dam Work?

The dam simply builds up a pressure head, similar to that produced by the weir that used to be located north of the bridge in Kilcullen, water being kept at a high level so it gains potential energy and can release that energy to do useful work as it falls. Work has a specific meaning in physics and is defined as "when a force moves a body through a distance". In this case, work is done when water loses momentum and creates a force as it decelerates on hitting turbine blades (just like a hammer head hitting a nail). Water is carried from the dam, under the N81, to the power house of the Poulaphouca Hydro Station, located several hundred metres away, via a 400 m long, 4.8 m diameter pressure tunnel and then via two penstocks or intake tunnels to the turbines. Two 15 MW Kaplan turbines at the generating plant produce electricity which is stepped up to a high voltage for transmission to a 110 kV substation near Stratford-on-Slaney.

How Does Kilcullen Get Its Power?

The Stratford substation, along with a 110 kV station near Walshestown in Newbridge supply electricity at 38 kV to the substation in Kilcullen. From this station, power is then distributed at a lower 10 kV to pole-mounted transformers (or cabinets in newer housing estates) around the town which finally reduce voltage to 230 V for domestic use. The idea of an electricity grid is to build redundancy into the system so power can find its way around "holes" in the grid (analogous to a fishing net). So if for instance Poulaphouca hydroelectric station becomes non-functional, the transformer station at Stratford is fed from elsewhere. Similarly for the Newbridge station. If the line from Stratford to Kilcullen breaks, or Stratford substation goes out of service, power is still fed to Kilcullen from Newbridge. Eirgrid, who control the transmission network for lines of 110 kV and over, can switch and sync generating stations into and out of the grid as demand rises and falls.

 

This is a map of the high voltage transmission network (high voltage being anything greater than 20 kV)

 

Image courtesy O'Dea Photograph Collection, The National Library of Ireland. Photographer James O'Dea

 

#industrialheritage

Iconic Items in the Science Museum, London

Some photos of iconic items in the Science Museum, London, taken when I was there in 2017: The Apollo 10 command module "Charlie Brown", complete with the effects of re-entry on the underside, A Saturn V second-stage engine, a cut-away of a Parsons steam turbine, and "Puffing Billy", the world's oldest steam locomotive.

Apollo 10 capsule "Charlie Brown" in the Science Museum, London © Eugene Brennan

 

Underside of Apollo 10 capsule "Charlie Brown"  © Eugene Brennan

Saturn V second stage engine © Eugene Brennan 

 

 

Parsons steam turbine © Eugene Brennan

"Puffing Billy", the world's first steam locomotive  © Eugene Brennan

 

 

Remembering Ernest Walton: Splitting the Atom

Public domain image via Wikimedia Commons

On 25th June, 1995, Ernest Walton, our only Nobel laureate for physics died in Belfast at the age of 91. Together with his colleague John Cockcroft, they built one of the first particle accelerators at the Cavendish Laboratory in Cambridge in the 1930s. This ultimately led to what's generally known as "splitting the atom". For this work, he was awarded along with Cockcroft a Nobel Prize in 1951.

Walton came to visit us in DIT, Kevin Street in Dublin when I was a student there in the mid 80s, and gave a lecture during which he spoke about his work in Cambridge. He appeared to be a mild mannered and unassuming man. I'm ashamed to say I didn't know who he was at the time. It was in an era before the Internet and our education system was hardly informative either. History books told us about the figures involved in revolution and the struggle for independence, but shamefully left out Walton, Hamilton and others involved in scientific discovery. I wish I could remember the content of Walton's lecture. I vaguely remember him talking about Ernest Rutherford, the New Zealand scientist who was also a pioneering researcher in the field of nuclear physics and radioactivity from the end of the 19th century onwards. Rutherford apparently had a larger than life personality and Cockcroft and Walton, his research students, used to wind him up.

Cockcroft and Walton's particle accelerator was one of the first machines for accelerating sub-atomic particles to high velocities so they would smash into atoms, breaking them apart. By studying what happened, scientists learned about the fundamental nature of matter. That work continues to this day, the 8.6 km diameter Large Hadron Collider located near Geneva, operated by CERN (European Organization for Nuclear Research) being immensely more powerful and capable of accelerating matter to almost the speed of light.

The Beginning of Radio Communication

Photo © Eugene Brennan

From one of the old books that belonged to my grandfather. A note in the appendix of a volume of the ICS reference library, 1905. If only they knew the developments that were to come in the future! In modern parlance, "the high-frequency transmission wave" is known as a carrier and the modification of the carrier by the superimposed wave is known as modulation. Sound waves having frequencies in the audible spectrum can't just be converted to an equivalent radio signal and transmitted. The frequency would be too low and for various technical reasons, including providing sufficient bandwidth for other channels broadcasting on and sharing the radio spectrum, and minimizing the size of antenna required, a technique called modulation is used. This is commonly either either amplitude modulation (AM) or frequency modulation (FM). The carrier is varied by a modulating signal derived from e.g. an amplified signal from a microphone, which changes the carrier's "size" (amplitude) or frequency. Originally, carriers were low, in the hundreds of kHz or somewhat lower. Carrier frequencies nowadays are vastly higher, typically 5 gigahertz (GHz) for WIFI and up to 108 MHz for normal radio broadcast programs on the FM band.

Photo © Eugene Brennan

 

Electromagnetic Induction and the Force on a Conductor in a Magnetic Field

A varying electrical current in the coil on the left produces a fluctuating magnetic field. This loops through the coil on the right, inducing an electrical current. Image by Ponor, CC BY-SA 4.0 via Wikimedia Commons.

 

Two principles, discovered in the early 19th century on which motors, generators and transformers work.

Electromagnetic Induction

Move a conductor (e.g. a piece of wire) in a magnetic field (produced by a magnet), or move the field and keep the conductor stationary or thirdly, vary the strength of the field. The result is that a current is induced in the conductor. This is how all electrical generators and transformers work, electricity being induced or generated in coils of wire as a magnetic field varies in strength. It's the main reason too why we use AC electricity for distribution.

Force on a Conductor in a Magnetic Field

Pass a current through a conductor placed in a magnetic field. The conductor experiences a force which tends to push it. This is the principle on which electric motors work.

Several scientists in the early 19th century made fundamental discoveries about the nature of electric currents and magnetic fields. Two of these were the Danish physicist Hans Christian Ørsted and the English scientist Michael Faraday. Faraday's apparatus including a transformer and motor can be seen in the Faraday Museum at the home of the Royal Institution in London.