Dr Kathy Romer answers your questions about Physics!

Asked this earlier, I'll ask again

Why do electrons behave the way they do when passed through double slits and behave like a wave, what actually happens?, and could you tell me how the act of measuring with a detector changes the results of this experiment? So strangeare there any other explanations for this besdies schrodinger's probablity ideas? and if this the most plausible expalantion could you explain it to me?thank you for your time

Reply 62

boyyo

6

Original post by Dr Kathy Romer

Good luck with your exam tomorrow!

I love the fact that you care so much about understanding the sign of your potential.

I hope this helps: Imagine a ball in your hand. Throw it vertically. If you define zero of vertical distance being at your hand, then it starts with zero potential energy (mgh, with h=0). But as it goes higher then potential energy gets larger up to a maximum at the top of its trajectory. Now move your vertical origin to the point where the ball has its maximum potential energy. So that means (mathematically) that potential energy is zero at the top of its trajectory. Likewise that means that when it falls back into your hand, its potential energy is negative.

Generalising this: we define the potential energy of a point mass (i.e. a very small mass) at an infinite distance from a big mass to be zero. That means the potential energy of that point mass at any smaller distance has to be negative.

Ahh okay, thats made it much clearer now! Thank you :smile:

Reply 63

Original post by ememoville

Why can't transformers use DC currents and also why is the induced current in the secondary coil the greatest when the power supply to the primary is being switched of?

Can you explain electromagnetic induction and how emf is induced and then why current is induced?

DC currents move electrons along at a constant velocity (give or take the electrostatic bumps they have with positive nuclei along the way).

It is only when charged particles accelerate (i.e. when their velocity is changing) that magnetic fields are generated. That is because accelerating charges produce electromagnetic radiation.

In an AC current, the velocity of the electrons changes because they move in one direction for half a cycle and in the opposite direction for the other half. But the current stays the same, i.e. the same number of electrons passes a give point in a second.

When the power is switched off, the velocity of the electrons almost instantaneously goes to zero. That is a very sudden negative acceleration and so you will get a spike in the magnetic field.

wrt EMF induction, see an earlier reply in this thread. wrt why current is induced when there is an induced EMF: if there are free charges they cannot help but move towards a location where their potential is lower. If you let a pound coin slip through your fingers it has to fall to the ground because nature prefers the lowest energy state. If an electron feels an emf it has to move in response. And all you need to have a current is a moving electron.

Reply 64

Original post by NatoHeadshot

Asked this earlier, I'll ask again

Why do electrons behave the way they do when passed through double slits and behave like a wave, what actually happens?, and could you tell me how the act of measuring with a detector changes the results of this experiment? So strangeare there any other explanations for this besdies schrodinger's probablity ideas? and if this the most plausible expalantion could you explain it to me?thank you for your time

Sorry I've not replied yet. I'll need my morning brain to explain quantum physics. I'll send you something tomorrow.

Reply 65

Original post by Dr Kathy Romer

Sorry I've not replied yet. I'll need my morning brain to explain quantum physics. I'll send you something tomorrow.

Alright sure thing! Looking forward to it

Reply 66

charlielao

5

Hi, I'm a year 12 student who's applying to uni this year and I'm really interested in nuclear fusion and planned on doing physics in uni and go on study further. Is there any books about nuclear fusion that is accessible to a high school student (not too hard for a high school student) Thank you

Also, what will you recommend me to study if i'm interested in nuclear fusion. Would it be nuclear engineering or pure physics. Thank you :smile:

Reply 67

Original post by Edminzodo

Hello Dr Romer,

I have quite a specific question if that's okay. I don't do Physics A-Level myself, but I'm very interested in it! So I was wondering, why does the fact that quarks have colour charge mean that they can only exist inside of other particles? Thank you so much! And this is a great thread! :biggrin:

Best regards,
Edminzodo

Dear Edminzodo, I was stumped by this one, but my friend and colleague Professor Antonella De Santo (http://www.sussex.ac.uk/profiles/221345) came to the rescue. Antonella is one of the leading scientists on the Large Hadron Collider, she told me:

"The short answer to your question re colour and confinement is: yes, due to the structure of the strong interaction Colour is the strong-force equivalent of the electric charge in electromagnetism. Quarks, antiquarks and gluons (the strong gorce carriers) are all "coloured". Quarks (and antiquarks) are never observed as free particles, but only in as bound states, known as hadrons (baryons = 3-quark states; mesons = quark-antiquark states). In simple terms, this happens because, in addition to the Coulomb-like part, the potential for the strong interaction also has a term that goes linearly with distance, which means that the strong force does not vanish at large distances. Quarks and antiquarks are always subject to an attractive force, which makes it impossible for them to "escape"."

Reply 68

Original post by charlielao

Hi, I'm a year 12 student who's applying to uni this year and I'm really interested in nuclear fusion and planned on doing physics in uni and go on study further. Is there any books about nuclear fusion that is accessible to a high school student (not too hard for a high school student) Thank you

Also, what will you recommend me to study if i'm interested in nuclear fusion. Would it be nuclear engineering or pure physics. Thank you :smile:

Hello Charlie,

Nuclear engineering tends to focus on Nuclear Fission, but look at some course descriptions in detail to see if any also cover Fusion.

In my experience, students with a strong background in either experimental or theoretical physics are able to join the UK wide doctoral (PhD) scheme in Fusion: http://www.fusion-cdt.ac.uk/
We have had several students from http://www.sussex.ac.uk/physics/ accepted to that program.

Kathy

Reply 69

Original post by NatoHeadshot

Asked this earlier, I'll ask again

Why do electrons behave the way they do when passed through double slits and behave like a wave, what actually happens?, and could you tell me how the act of measuring with a detector changes the results of this experiment? So strangeare there any other explanations for this besdies schrodinger's probablity ideas? and if this the most plausible expalantion could you explain it to me?thank you for your time

Hello,

Even with my morning brain, I knew I couldn't give you a satisfactory answer. So I went to Mr Schrodinger's Cat himself: the legendary @johngribbin ! This is his awesome reply:

"The short answer is, nobody knows. Richard Feynman said "nobody understands quantum mechanics". And he got a Nobel Prize for it! He called the double slit experiment "the central mystery", and I discuss it in my Kindle single The Quantum Mystery (£1.99, cheaper than a cup of coffee).https://www.amazon.co.uk/Quantum-Mystery-Kindle-Single-ebook/dp/B01AYA4BYQ/ref=sr_1_1?s=books&ie=UTF8&qid=1466446636&sr=1-1&keywords=quantum+mystery
The "collapse" idea is out of date and just one of several interpretations. I favour many worlds. https://en.wikipedia.org/wiki/Quantum_Reality"
Thanks John!!

Reply 70

Hi,

I'm a year 12 student hoping to do a Physics degree at uni. What reading would you recommend to someone hoping to expand their knowledge of Physics? I've found a few books on Physics at my local library but they all seem too complicated, so I'm looking for books that aren't in layman terms but aren't in PhD terms either.

Thanks

Reply 71

OliverGuy

Original post by Fox Corner

Struggling with a particular theory for your exams? Wondering whether to study Physics at a higher level? Just got a question about the subject in general? :confused:

We're pleased to welcome Dr Kathy Romer to the site for a Q&A session next Tuesday. Kathy is a reader in Astrophysics at Sussex University and a Public Engagement Fellow for the Science and Technology Research Council. She completed her PhD at the University of Edinburgh in The Large Scale Distribution of X-ray Clusters of Galaxies, and is a world expert in the discovery and exploitation of X-Ray clusters of galaxies. :smartass:

Dr Kathy Romer will be answering your questions up until Tuesday 21st June at 6pm.

Post your questions below, and Kathy will try and answer as many as possible. :thumbsup:

With the Crooks Radiometer where does the force that makes it spin come from? I knows its from the infrared radiation being given out, but does this really have force? And if so how big is it and what real world effects does the force have?

Reply 72

Original post by DarkEnergy

Hi,

I'm a year 12 student hoping to do a Physics degree at uni. What reading would you recommend to someone hoping to expand their knowledge of Physics? I've found a few books on Physics at my local library but they all seem too complicated, so I'm looking for books that aren't in layman terms but aren't in PhD terms either.

Thanks

Hi I'm planning to do physics to :biggrin:

what unis are you applying to this For 2017 entry. Also have you tried a brief history of time by Stephen hawking?

Reply 73

Original post by NatoHeadshot

Hi I'm planning to do physics to :biggrin:

what unis are you applying to this For 2017 entry. Also have you tried a brief history of time by Stephen hawking?

Hey, I'm planning to apply to do an MPhys at York, BsC (joint honours) Computer Science and Physics at Edinburgh and Queen's University Belfast, and I'm honestly not sure about the other two. Honestly depends on my AS results. If I get AAAA I'll probably throw in an application to Oxbridge, otherwise I'll be realistic. How about you?

Also thanks, will check out that book.

(edited 7 years ago)

Reply 74

Original post by DarkEnergy

Hey, I'm planning to apply to do an MPhys at York, BsC (joint honours) Computer Science and Physics at Edinburgh and Queen's University Belfast, and I'm honestly not sure about the other two. Honestly depends on my AS results. If I get AAAA I'll probably throw in an application to Oxbridge, otherwise I'll be realistic. How about you?

Also thanks, will check out that book.

That's interesting I never knew that they did a joint honors that sounds quite handy. I had decided on queens imperial Oxford St. Andrews and Manchester I think but now I'm not sure about either but I am preparing for the PAT for Oxford already on November well my preparation is slow rn but it should kick in by next week or so
I hope you smash your AS! I'm only going to have my maths AS results in August and I'm going to have to use predicted grades for the rest, hopefully no nasty suprises on my math grade

Reply 75

Original post by NatoHeadshot

That's interesting I never knew that they did a joint honors that sounds quite handy. I had decided on queens imperial Oxford St. Andrews and Manchester I think but now I'm not sure about either but I am preparing for the PAT for Oxford already on November well my preparation is slow rn but it should kick in by next week or so
I hope you smash your AS! I'm only going to have my maths AS results in August and I'm going to have to use predicted grades for the rest, hopefully no nasty suprises on my math grade

Thanks, that's very kind of you.

That's a nice selection of unis you picked out, good luck on the PAT mate.

Reply 76

Original post by DarkEnergy

Thanks, that's very kind of you.

That's a nice selection of unis you picked out, good luck on the PAT mate.

Thanks mate, are you going to be using a2 predicted grades or AS I'm not sure how it works I live in Dubai :tongue:

Reply 77

Original post by NatoHeadshot

Thanks mate, are you going to be using a2 predicted grades or AS I'm not sure how it works I live in Dubai :tongue:

My A2 predicted grades are going to be based off my AS results (i.e. A2 predicted grade = 1 grade above AS grade in that subject) although in my UCAS application pretty sure I'll include both anyways.

Reply 78

Hello again everyone.

I apologise for being silent for a few days. Its been a particularly intense week wrt my role in the darkenergysurvey.org but things are calming down now. All questions that were posed before 6pm on Tuesday will be answered in the order they arrived. I've had a scan through and I don't see any related to A2 exams later this week, but if you did post one and haven't had an answer, please ping me and I'll respond asap.

Kathy

Reply 79

oShahpo