How to approach a Physics Viva/SOE

Physics Vivas can be daunting.

As with any viva, physics vivas can frighten people. The key with them is to try and keep a level head.

I tell all the people I VIVA to remember to do this: As you walk from the waiting/briefing room before the exam to the examination hall, look on your left. There is a room with a big meeting table which has a glass wall to the corridor.

Look on this table and pay attention. You’ll see loads of textbooks open on certain pages. Why? Because even the examiners need a refresher in what they are examining.

Remember you’ve been working (hard) on this stuff for months. There is a high likelihood that you know more than the examiner, particularly in the basic sciences. They probably haven’t learnt this in depth for many years.

Physics Vivas are Predictable.

The physics curriculum has the advantage of being fairly contained. There isn’t much that can come up that isn’t predictable.

Look at anything in your anaesthetic room, the examiners can (and will!) ask about it. Well maybe not your flashy coffee mug. Think if you can answer the following:

  1. What is it?
  2. What is it used for?
  3. How does it work? (First principles, through to specifics)
  4. What are its limitations and sources of error?

If you can do this for everything then you’ll pass easily.

When I told an SHO I work with this they asked me about where the gas laws apply. Everything in the curriculum has a clinical application. That’s the whole point. If you’ve rope learnt the gas laws, but don’t understand the application, you’ve missed the point. Go and look at it again and concentrate on its application rather than the ‘pure’ science. You’ll remember it better if its application to your every day job makes sense.

The Layout of a typical Viva.

Note: Not all vivas are laid out like this, but most follow these principles

  1. The definition.
  2. The explanation of a principle.
  3. The clinical application of the above principle.

So if we take an example (a favourite of mine)

  1. What is capacitance? and what is its unit?
  2. Explain how a capacitor stores electrical charge.
  3. How does a defibrillator work?

The Definition

Now, when you’re doing a definition, stop and think. The definition sets the tone for the rest of the viva. Are you a clear pass from the first sentence? or are you playing catch up? Make your answer one sentence and punchy. Make the examiner think you know your stuff:

‘Capacitance is a measure of a capacitors ability to store electrical charge. Its unit is the Farad, which is defined as the ability to store one coulomb of charge when one volt is applied across the capacitor.’

There, you obviously know your stuff. Don’t do what many people do and go into a description of how a capacitor works.

Well a capacitor works when electrons go onto one plate and can’t get across to the other side. This makes it negatively charged and then electrons from the other plate….

Doesn’t sound great does it? You have yet to answer the question set to you. After your 2-3 minute speech on the inner workings of a capacitor the examiner calmly asks…. So, What is capacitance? and what is its unit?

He/She is now annoyed. You are playing catch up. You’ve also wasted a few minutes.

Physics is based around definitions. Learn them and practice them. They should be precise, accurate and above all, Punchy.

Like most vivas, if they think you obviously know this, they move on quicker. You can sometimes be lucky and avoid an explanation if your definitions are good!

The Explanation

So you’ve impressed with your punchy definition and the examiner has a little smile coming. This person knows their stuff…. Keep it going.

When explaining the principle, start basic. Diagrams help, as long as you can talk whilst drawing. The art is being able to build a diagram whilst explaining the principle.

Take this example. Draw a simple diagram of a capacitor and explain how its made up:

A capacitor is made up of two conducting plates, sandwiching a non conducting dialetric material…

Simple, gets the point across. If you really know your stuff you could comment about typical materials each is made from, but it really isn’t required. If you can talk about the diagram as you are drawing it in a structured way, it helps ease that awkward silence and also allows you to show off your in depth knowledge.

Then move onto how it actually works now you have a basic diagram

If we apply a direct current to the capacitor, initially electrons will settle on the first plate. They are unable to pass over the non conducting dialetric material to the second plate, so the first plate becomes negatively charged. This then repels electrons electrons off the second plate and initially allows current to flow. As the second plate exhausts its supply of electrons, the current flow will slow and eventually cease….

As you’re explaining this, draw it on your diagram. Then add in the graph to show the current flow decline. Show that examiner you know what you’re talking about.

Now, its the crossroads. If you know your stuff you’ll realise this viva is going in one of two directions.

Either, Its going to go to defibrillators, or its going down the line of differences in current flow with DC vs AC current. This is why you should stop here, and not go into any more depth. Let the examiner guide you through where they want to go. There is a fine line between appearing confident and talking fluently and going off on a tangent. As a rule of thumb, if you’re talking for more than 90-120 seconds, stop and let the examiner guide you.

The Clinical Application

This section is all about how we it is used in day to day clinical practice. How does a capacitor factor into your day to day practice in this case?

This is likely to go down the line of a defibrillator as this is the most common device talked about. But they may go on to talk about filters, so keep an open mind.

Keep the explanation simple. Draw a simple defibrillator diagram and be guided by the examiner as to where they want to go.

When you’re revising

When you’re revising think how they can ask you this stuff in a viva. Yes, even when you’re revising for the MCQ exam.

Think about how you’d explain how these things work when you’re learning about them. If you learn this stuff in groups and explain them to each other when revising for the MCQ you can get a nice head start for the VIVA.

Remember that first impressions are highly important in exams.

That first sentence will make the difference. Everyone always tells people going to the VIVA to pause and think before opening their mouth. This is so true!

Remember that in Physics, the first sentence is likely to include some kind of definition. So if you learn one thing well, make it the definitions.


By the way, If you’re wondering what the picture at the top of this post is, Its the pass sheet from a Final Viva (the one from my viva incidentally!). That’s the aim of all this stuff, to get that sheet with your number on it…

© Sam Beckett and Physics4FRCA, 2018. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited.

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