Author Archives: mrmackenzie

charged particles in magnetic fields⤴

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These Bitesize pages will help if you need to recap on the basics of magnets.  A magnetic field is produced whenever current flows through a wire.  The magnetic field is represented by a series of concentric circles around the wire, as shown below. Magnetic field lines around a current carrying wire.  image: physick wiki The direction … Read more

particles in electric fields⤴

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An electric field can be used to accelerate charged particles.  Conservation of energy tells us that the work done by the field is equal to the change in the particle’s kinetic energy.  The speed of the particle can be determined if its charge and the accelerating voltage are known.  These notes show how to perform the calculation. … Read more

forces⤴

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We’ve been looking at forces for the past two weeks. Here are some notes and videos to help you learn more about this topic. Newton’s 1st Law animation showing effects of air resistance Friction: here are 3 clips about friction from the BBC programme Bang goes the Theory //www.youtube.com/watch?v=qhpXnGaYmdA //www.youtube.com/watch?v=XNOEP1XIFiM and look what happens when … Read more

fundamental particles: quarks, leptons and the standard model⤴

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At the end of Our Dynamic Universe, we considered big things like stars, galaxies and the Universe itself.  Now the Particles and Waves unit brings us to particles so small we need groups of them just to make a single atom.  Is there a connection? Why do we study particles? from mr mackenzie on Vimeo.  The Standard Model An elementary … Read more

dark matter, dark energy and the end of the Universe⤴

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It’s complicated and cosmologists are not certain.  One of the issues is only being able to see about 4% of the mass in the universe – the stars, planets, gas and dust.  About 25% of the mass of the universe is Dark Matter.  It’s “dark” because it doesn’t emit light that enables us to see … Read more

evidence supporting the Big Bang model: 3. Olber’s paradox⤴

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You might remember that we looked at some paradoxes when we studied special relativity earlier this term.  Here is another situation where a paradox can arise.  The German astronomer Heinrich Olbers (1758–1840) asked why the night sky was dark.  At the time, astronomers believed that the Universe was both infinite and steady state (unchanging), so … Read more

evidence supporting the Big Bang model: 2. nucleosynthesis⤴

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As we worked through the diagram explaining the stages of the Big Bang model, we looked at a section of the diagram where the Universe was hot enough for nuclear fusion.  At this point, hydrogen nuclei were fusing together with other hydrogen nuclei to create helium nuclei.  As the Universe expanded, it cooled and further … Read more

evidence supporting the Big Bang model: 1. CMBR⤴

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introduction to the Big Bang from mr mackenzie on Vimeo. Georges Lemaître’s theory of an expanding Universe, which has become known as the Big Bang, was supported by Hubble’s observations.  The expanding Universe idea was challenged by influential scientists who believed the Universe was both infinite (and therefore not expanding) and steady state (unchanging).  Supporters … Read more