Category Archives: Teaching

Summer hols; summer school, swimming and that book

You must be finished for the summer? Like most academics, I get asked this question every day in summer, usually by village acquaintances convinced that college closes the day the students finish their exams.

Some lecturers in the Institutes of Technology do indeed take off from June 20th to September 1st; that is their right, given the heavy teaching load during termtime. However, for those of us who try to keep up the research, the summer months are the time to get something done, just like our colleagues in the universities.

For me, this is no chore  – the sheer bliss of being able to do quiet research without classes, meetings, staff interactions and all the rest of it. Very restful. Also, we’re having a serious heatwave in Ireland this month and I’m happy to escape to the cool, quiet office every day. So I plug away happily during the day and treat myself to a swim in my village in the evenings..

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Tide’s in on Lawlor’s Strand in Dunmore East

Actually, I did give some ‘cameo’ lectures this week and last, to our summer school. We have a very nice bunch of engineering, computing and business students visiting from Kiel in Germany, and I had fun trying to condense my climate science course down to a one-hour presentation for each group. I haven’t given short presentations on climate before, it was very satisfying to prepare (see here for a copy of the talk)  The other thing I noticed was that students from the continent always seem to be very mature, polite and interested. I must look into an exchange sometime, do they have Erasmus for staff?

My main task this summer is to finish my little book on cosmology. It’s based on a course I have taught for some years and it’s been a lot of fun to write. Now I’m finding that it’s one thing to write a book and quite another to get it published! Still, I have plenty of time now to be writing book proposals and writing to publishers. In the meantime, I look forward to a swim in the sea everyday after work and a walk into the village. It’s funny to live in a village where others come for summer holidays!

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Tide’s out on Lawlor’s Strand in Dunmore East

Update

Unfortunately it’s so warm, we’re beginning to get quite a few jellyfish. Hope it cools down a little next week!

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A day in the life

There is a day-in-the life profile of me in today’s Irish Times, Ireland’s newspaper of record. I’m very pleased with it, I like the title  – Labs, lectures and luring young people into scence  – and the accompanying photo, it looks like I’m about to burst into song! This is a weekly series where an academic describes their working week, so I give a day-to-day description of the challenge of balancing teaching and research at my college Waterford Institute of Technology in Ireland.

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Is this person singing?

There is quite  a lot of discussion in Ireland at the moment concerning the role of  institutes of technology vs that of universities. I quite like the two-tier system – the institutes function like polytechnics and tend to be smaller and offer more practical programmes than the universities. However, WIT is something of an anomaly – because it  is the only third level college in a largeish city and surrounding area, it has been functioning rather like a university for many years (i.e. has a very broad range of programmes, quite high entry points and is reasonably research-active). The college is currently being considered for technological university status, but many commentators oppose the idea of an upgrade – there are fears of a domino effect amongst the other 12 institutes, giving Ireland far too many universities.

It’s hard to know the best solution but I’m not complaining – I like the broad teaching portfolio of the IoTs, and there is a lot to be said for a college where you do research if you want to, not because you have to!

Update

I had originally said that the institutes cater for a ‘slightly lower level of student’. Oops! This is simply not true in the case of WIT, given the entry points for many of the courses I teach, apologies Jamie and Susie. Again, I think the points are a reflection of the fact that WIT has been functioning rather like a university simply because of where it is.

Comments on the article are on the Irish Times page

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Resistors in series and parallel

In the last post, we saw that for many materials, the electric current I through a device is proportional to the voltage V applied to it, and inversely proportional its resistance, i.e. I = V/R (Ohm’s law). If there is more than one device (or resistor) in a circuit, the current through each also depends on how the resistors are connected, i.e., whether they are connected in series or in parallel.

In a series circuit (below), the resistors are connected one after the other (just as in a TV series, one watches one episode after another). The same current runs through each device since there is no alternative path or branch, i.e.  I = I1 = I2. From V = IR, we see the voltage across each device will be different; in fact, the largest voltage drop will be across the largest resistance (just as the largest energy drop occurs across the largest waterfall in a river). The total voltage in a series circuit is the sum of the individual voltages, i.e. V = V1+V2. As you might expect, the total resistance (or load) of the circuit is the simply the sum of the individual resistances, R = R1 + R2.

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Series circuit: the current is the same in each lamp while there may be a different voltage drop across each (V = V1+V2 +V3)

On the other hand, resistors in a circuit can be connected in parallel (see below). In this case, each device is connected directly to the terminals of the voltage source and therefore experiences the same voltage (V = V1=V2). Since I = V/R , there will be a different current through each device (unless they happen to be of equal resistance) .The total current in a parallel circuit is the sum of the individual currents, i.e. I = I1+I2. A strange aspect of parallel circuits is that the total resistance of the circuit is lowered as you add in more devices (1/R = 1/r1 + 1/r2). The physical reason is that you are increasing the number of alternate paths the current can take.

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Parallel circuit: the voltage is the same across each lamp but the currents may be different (I = I1+I2)

Confusing? The simple rule is that in a series circuit, the current is everywhere the same because there are no branches. On the other hand, devices connected in parallel see an identical voltage. In everyday circuits, electrical devices such as kettles, TVs and computers are connected in parallel to each other because it is safer if each device sees the same voltage source; it also turns out to be more efficient from the point of view of power consumption (an AC voltage is used, more on this later).

In the lab, circuits often contain some devices connected in series, others in parallel. In order to calculate the current through a given device, redraw the circuit with any resistors in parallel replaced with the equivalent resistance in series, and analyse the resulting series circuit.

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Problem

Assuming a resistance of 100 Ohms for each of the resistors in the combination circuit above, calculate the total resistance of the circuit. If a DC voltage of 12 V is applied, calculate the current in the circuit. (Ans: 133 Ω, 0.09 A)

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Current, voltage and the French resistance

Last week, our 1st science students had their first laboratory session on electrical circuits. They haven’t met electricity in lectures yet, so I spent some time explaining the concepts of current and voltage.

In essence, current is the flow of electric charge around a circuit (measured in amps) while voltage is the energy that drives the current (and is measured in volts). I find it helpful to think of the two in terms of cause and effect; a current will only flow in the circuit if a voltage is applied. In simple circuits, this energy is supplied in the form of a DC battery (or voltage source) that drives the current through some device (or resistor) in the circuit.

Let's Explore Science... Turn on the Light

The lamp (or resistor) lights as the current goes through it, completing the circuit

You might expect that there is a simple relation between voltage and current, and sure enough, the German scientist Georg Ohm discovered that, for many materials, there is a linear relationship between the two. Ohm’s law states that the current I passing through a material connected to a voltage V is given by the simple equation I = V/R. Here, 1/R is the constant of proportionality and is called electrical resistance and you can see why from the equation: a material with a very large value of R will pass almost no current (bad conductor), while a material with very small R will yield a large current for the same voltage (good conductor). So the term has exactly the same meaning as it has in ordinary speech, e.g. the French resistance. Resistance is measured in volts per amp, also known as Ohms (Ω).

Voltage_vs._Current

Many materials have a linear relation between voltage and current – the slope of the graph is the material’s resistance

In the experiment, the students apply a series of voltages to an unknown resistance in a circuit, and record the corresponding currents. A plot of voltage versus current then allows them to verify the linearity of the relation and the resistance is estimated from the slope of the line. (Strictly speaking, one should really put the voltage on the x-axis as it is the independent variable, but the calculation is simpler if the voltage is on the y-axis).

Measuring current and voltage

All of the above is fine in principle. Yet novices find the measurements quite difficult in practice. They have problems connecting the circuit because they get confused between measuring the current that flows through a device, and the voltage across it. It’s crucial to understand the difference between the two, and I suspect the modern multimeter adds to the confusion.

simple-circuit-diagram

The ammeter reads the current running through the resistor while the voltmeter reads the voltage across it. A plot of voltage vs current gives a measurement of the resistance

When I was a student, the current was measured by passing the current through an ammeter (marked A in the diagram), an analog device with a nice big dial calibrated in amps or milliamps. The voltage across the resistor was measured by connecting a different instrument, the voltmeter, across the terminals of the resistor; this voltmeter was a separate meter with a dial calibrated in volts (marked V in the diagram). So an ammeter was always connected in series with the resistor/device, while the voltmeter was always connected across it (in parallel).

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Current is measured by passing it through the ammeter (L) while voltage is measured by connecting across the voltmeter (R)

Nowadays, identical instruments are used for both; to measure current, one passes the current through the terminals marked ‘current’ of a multimeter, and the main dial on the meter is switched to the amp scale. To measure voltage, one connects the ends of the resistor across the terminals marked ‘voltage’ on an identical multimeter, and the dial is switched to volts. It sounds simple, but it’s easy to connect to the wrong terminals, getting no readings or blowing the fuse in the meter. More subtly, I think the clever circuity inside the multimeter hides the fact that current goes through while voltage drops across. All in all, I suspect students would understand circuits better if  we went back to separate instruments for measuring current and voltage….

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The mysterious multimeter. To measure current, leads are connected to the sockets marked ‘common’ and ‘amps'; to measure voltage, one connects to the sockets marked ‘common’ and ‘voltage’.

Notes

1. If a 12-V voltage is applied across a resistor of 15, what current flows in the circuit? How many electrons per second does this current represent? (Ans: 0.8 mA,  5.0 x 1015 electrons)

2. What happens to the current if one end of the resistor accidentally touches the other? (Ans: the circuit resistance drops almost to zero and the current becomes very large – don’t try this in the lab!)

3. Ohm’s law is a misnomer – it is not a universal law of nature but simply a property of some materials (many materials have a nonlinear response to voltage, including your cat).

4. It might seem from Ohm’s law that a material with zero resistance can give infinite current! No such materials are known; the relation is simply not valid for these materials. However, some materials have extremely low resistance at very low temperatures, known as superconductors. A good application of superconductivity can be found at the Large Hadron Collider, where protons are guided around the ring by magnets made of superconducting material: this reduces power consumption enormously but the snag is that the entire accelerator has to be kept at extremely low temperatures during the experiments.

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End of semester

This week is one of my favourites in the college timetable. The teaching semester finished last Friday and the hapless students are now starting their Christmas exams. It’s time to empty out the teaching briefcase and catch up on research…

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Examtime in college

I recently compiled a list of this semseter’s research and outreach and was pleasantly surprised – three conference presentations, two academic papers and eight public lectures , not to mention a couple of science articles and book reviews in The Irish Times (see here for presentations and here for articles).

All of this is on top of an 18-hour teaching week, which adds up to a lot of late nights. I’ve been arguing for years that the workload in the Institutes of Technology should be more flexible; it’s very difficult to do any meaningful research if you’re teaching 18 hours a week. Another challenge is that most lecturers in the IoT sector are 3-4 to an office, with consequent staff interactions, phone calls and students coming to the door. As a result, a great many lecturers simply stop doing research, which is a terrible waste and hardly ideal for a college that teaches to degree level and beyond. I often think that, far from enhancing ‘productivity’, work practices in the IoT sector mitigate strongly against good teaching and research at third level.

In my case, I stay in college most evenings until 9 pm. That said, I enjoy the research – as I say to my students, if you find a job you truly like, you’ll never work a day in your life!

I’m particularly pleased with my recent paper on the discovery of the expanding universe. It’s my first foray into the history of cosmology, and it has already got quite a bit of attention,  thanks to a very nice conference in Arizona. I very nearly didn’t go to this conference because of teaching commitments; now I’m glad I did as it was a lot of fun and the paper has opened quite a few doors. These days, I turn down far more opportunities than I accept, it may finally be time to consider an academic move.

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Slipher’s telescope at the Lowell Observatory in Flagstaff, Arizona

Update

Meanwhile, rumours continue to circulate in the media concerning the prospect of our college being turned into a technological university. This would certainly be a welcome development, especially if it meant reduced teaching for those engaged in research, but I’d be quite surprised. WIT has been very successful at attracting research funding in certain areas, but research activity per academic is quite low in our college in comparison with the university sector. I don’t see how we could qualify as a university without bringing in quite a lot of new research-active staff , a buy-in for which there is no money whatsoever; hopefully I’m wrong on this.

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Frontiers of Physics 2012 at Trinity College Dublin

I spent last weekend at the Frontiers of Physics conference at Trinity College Dublin. This is an annual meeting hosted by the Institute of Physics in Ireland; the aim is to establish links with secondary schools all over the country and to present the latest developments in physics and physics teaching. This year it was Trinity’s turn to host the conference and it was excellent, not least due to the superb organisation of IoP teaching coordinators Paul Nugent and David Keenahan.

Saturday morning featured some great lectures in the historic Schrödinger lecture theatre, located in the Fitzgerald building of Trinity’s School of Physics. Visiting this building always feels like coming home for me, as I did my PhD in one of the labs downstairs and gave tutorials in the Schrödinger theatre as a postgrad. The library on the second floor of the Fitzgerald building is becoming a notable science museum, with exhibits for many great scientists associated with Trinity such as Preston, Joly, Fitzgerald and Walton. (Schrödinger himself was a Professor at the Dublin Institute for Advanced Studies, not Trinity, but the theatre is named after the famous ‘What is Life? ‘ series of public lectures he gave there there).

The Schrödinger lecture theatre on the top floor of the Fitzgerald building

The Fitzgerald building, home to the physics department at TCD. The bubbles are a mockup of a sculpture that will honour the department’s Nobel laureate Ernest Walton

I won’t describe the lectures in detail, but three stood out for me:  ‘Tuning in the radio sun’, a description of solar astronomy at Birr Castle by Prof Peter Gallagher, head of the solar physics group at Trinity: ‘Tiny but mighty’ , a superb introductory lecture on nanotechnology by Prof Jonathan Coleman, head of the low-dimensional nanostructures group at Trinity: and ‘CERN, the LHC and the Higgs boson’  by Steve Myers, director of accelerators and technology at CERN.

Yes, that Steve Myers, the Belfast-born director of accelerators at CERN. Steve gives great talks on the nuts-and-bolts of the Large Hadron Collider and this was the main reason I was at the meeting. I’m scheduled to give yet another talk on the Higgs boson next month, so it’s important to catch lectures like this whenever I can. There’s nothing like hearing details of the experiment from the horse’s mouth and Steve certainly didn’t disappoint.

Steve Myers in action at the conference

On the teaching of physics, Dr Karen Bultitude of University College London gave an interesting lecture on ‘Gender Aware Teaching Practice’. As everyone in the discipline knows, a marked gender imbalance persists amongst students choosing physics; Karen’s main point was that all of the research done in this area indicates that making physics more ‘girly’ simply does not work, and she had some important tips for making physics more approachable for both genders. (Once more, it raises the question how a certain video at the European Comission ever saw the light of day, but let’s not go there).

After the lectures, we were treated to lunch in Trinity Dining Hall;  I think those who had not visited the college before were blown away by the Hall and by the walk across Front Square. Maybe I notice this sort of thing more after another trip to the US (see previous post), but the best was yet to come..

The Dining Hall at Trinity

Front Square at Trinity College

After lunch, we were treated to an exhibition of Walton memorabilia by  Dr Eric Finch. (Ernest Walton, a former Head of Physics at Trinity, won a Nobel prize for splitting the atomic nucleus with Cockroft in 1932). Eric had many fascinating things to show us, not least the famous letter where the brilliant young scientist describes his ‘red-letter day’ to his fiancee. Best of all, the exhibition is currently situated in Trinity’s Long Room, one of the most famous libraries in the world and a sight well worth seeing in it’s own right.

Dr Eric Finch at the Walton exhibit in the Long Room

The Long Room at TCD – it really is like this

Finally, we all trooped back to the physics department to see the Monck observatory. Since my time at the college, an observatory has been installed on the roof of the Fitzgerald building, consisting of an Atmospheric and Space Weather Monitor (outside radio antenna) and a Schmitt reflecting telescope (inside the dome, see below). Brian Espey, Professor of astrophysics at TCD,  described the operation of the telescope and we each had a peep. The observatory must be one of the most centrally located telescopes anywhere in the world- however, apparently the light pollution is not as bad as you might expect because the college is a quiet island in the centre of the city at night. I’m told the main problem is the use of floodlights for rugby practice!

The new dome on top of the Fitzgerald building

The Schmitt reflector inside the dome

The radio antenna for atmospheric measurements

All in all, a great meeting in a superb setting. The Frontiers conference takes place in a different venue each year, but it’s hard to compete with 400 years of history…

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You must be on your holidays now

You must be on your holidays now? I’m confronted with this question/accusation every time I go shopping in my village these days. Almost everyone I know assumes that lecturers merely teach and the summer holidays are ours to enjoy at our leisure.

I never know how to correct this misapprehension. Usually, I just nod amiably – after all, the main thing is that I have a job I really enjoy doing. However, it worries me that there is such widespread misunderstanding of academia. Occasionally, I try to explain that ‘holiday-time’ is in fact the only time I get to do any research. However, I usually get the feeling the questioner either doesn’t believe me or thinks I’m a fool for not putting our generous holidays to good use.

And the official holidays are generous, there’s no question. In the Institutes of Technology, staff do not have to report formally for work from June 20th to September 1st. It sounds great, doesn’t it? But for those engaged in research at any level (and it’s very difficult to get a job teaching to degree or master’s level if you are not engaged in some sort of research), this is the only time such work gets done.

In my case, I used to head back to my alma mater Trinity College as soon as term ended, doing experimental work in the magnetic resonance lab. These days, I’m more involved in writing science. This summer, I’m working on a book on cosmology, aimed at a popular audience. I started it last summer at Harvard and have been tipping away whenever I can during a very busy semester. Now I have a good opportunity to finish. I don’t think of this as a chore; like most academics, I see this sort of work as an important part of my job and it’s very satisfying. I really like working in the college over the summer months, it’s a very nice environment of quiet academic activity.

I also have two conferences in August and next month I’m giving a public talk on Irish astronomy and the big bang. So it’ll be a busy summer, which doesn’t bother me in the slightest as long as I get away for the odd weekend. As for travel, I’m coming round to the view that most countries are simply too hot for me in the summer and I like the variability of Irish weather. I’ll take a few weekends in the west coast of Ireland, playing tunes in the pubs at night and surfing during the day, that’ll do nicely…

It’s a tough life – Ed

Update

This blog has been nominated for an award, the Three Quarks Daily 2012 Awards. If you like the blog, why not throw in a vote here.  That said, there are some great blogs on the nominee page, I’m having fun browsing them all

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