Category: A Level Physics Chapters

Introduction to GCE Physics (7407/ 7408)

This selection of resources should set you off on the correct the path from your first lesson. Most of the files can be obtained freely on the internet but these directly relate to what you will do over the two years of GCE Physics.

The first thing to  know is that if you have been directed to this page your teacher will be doing AQA Spec A Physics (there is also a Spec B). This means you are in fact studying  a course with AQA the code for it is “7407” for AS and “7408” for A2. This document tells you all about what you need to know and how the course is structured.

Specification  (Full details for parents, pupils and teachers)

Key Ideas / Exams

Core content

• 1 Measurements and their errors
• 3 Waves
• 4 Mechanics and materials
• 5 Electricity
• 6 Further mechanics and thermal physics
• 7 Fields and their consequences
• 8 Nuclear physics

Options (one of these is chosen)

• 9 Astrophysics
• 10 Medical physics
• 11 Engineering physics
• 12 Turning points in physics
• 13 Electronics

General Documents

Advancing Physics Equation Help (an alternative board formulae sheet – good for general use)

Best Pocket Handbook IOP (some formulae presented nicely)

Casio Calculator Manual (example for Casio in case you needed one and lost it)

Glossary of Terms (Terms specific to GCE Physics in particular to use in ISA exams and general exams)

Resources to Work on

0 Skills in AS Physics (PPT Resources on Practical / Maths Skills)

Problems-1-Trigonometry  (You must be able to do trig for Physics AS/A2 try some out here)

sin cos tan (more on Trig)

Problems 2 Formula (You must also be able to rearrange formulae without regard to their actual values test yourself out)

Problems 3 Skills Worksheet (This sheet tests if you understand how to convert quantities)  skills_data_sheet (this helps with Problem sheet 3)

Working with Errors (Simple PPT for starting to look at errors)

Problems 4 Uncertainty (Sheet on Lab uncertainty)

Cross Winds Calculations..

Try out this game which is all about defeating a cross wind…

Bowman Game

This one is all about the angles and the Kinematics, looks simple but think about projectile motion…

https://www.animatedscience.co.uk/fun/bowman.swf

8 Equations of Motion…

A common problem for teaching Physics when you are not a Physics teacher is that you make many mistakes with complex ideas which appear simple on the surface.

I drop a ball to the earth and want to work out the distance fallen in a certain time. I then do a calculation of..

distance x speed = time

Oh dear but when I do the experiment it does not work like that but it works like this…

[latex size=”3″]s =\frac{1}{2}at^{2}[/latex]

Now we can reason this out. If I allow a ball to fall to earth it must accelerate due to the field of gravity around the earth 9.81N/kg. Or 9.81 m/s/s.

But where does the formulae  come from that we general use?

[latex size=”3″]s = ut+\frac{1}{2}at^{2}[/latex]

1. s = the distance between initial and final positions (displacement) (sometimes denoted as x)
2. u = the initial velocity (speed in a given direction)
3. v = the final velocity
4. a = the constant acceleration
5. t = the time taken to move from the initial state to the final state

So the question is what is it all about.

Well we need to think way back to the idea of a simple idea of how to work out the distance travelled by  a runner in a race.

Think of an athlete travelling 100m in 10s at a constant speed. His velocity or speed is…

[latex size=”3″] \frac{d}{t}= speed[/latex]  OR  [latex size=”3″] \frac{s}{t}= v[/latex]

Now this works fine if we are travelling at a constant speed but hey as you know this is not always the case and sometimes an object has a constant acceleration or deceleration. If you think about a graph of a person who got faster and faster then we would have a slope or triangular area on a speed-time or velocity-time graph. Now the area under the graph would be the distance travelled on the journey. But if our speed changed s=vt (for constant speed) becomes….

[latex size=”3″] s=\frac{vt}{2}[/latex]

Now you have an expression for the average speed but only from a standing start. Imagine now the same velocity time graph but this time the runner was already travelling at a velocity at the start of timing. Our area would become a triangle and rectangle…

[latex size=”3″] s=\frac{(v-u)t}{2}+ut[/latex]

Simplifies to

[latex size=”3″] s=\frac{(v+u)t}{2}[/latex]  – Eq 2

This is the formulae for average speed that takes care of all situations even when u or v is 0. Now then think graphically again if we are travelling at an initial velocity and then accelerate we are back to triangle and square again when looking at a vt graph. Hence…

[latex size=”3″] v=u+at[/latex]  – Eq 1

Now we can use this in a rearranged form..

[latex size=”3″] t=\frac{(v-u)}{a}[/latex]

Substitute into Eq 1 in new form into 1 to remove t so we now have an expression…

[latex size=”3″] s=\frac{(v+u)}{2}*\frac{(v-u)}{a} [/latex]

Which simplifies to..

[latex size=”3″] s=\frac{(v^{2}-u^{2})}{2a} [/latex]  – Equ 4

Now we have this we can work also work backwards to get Eq 3 …

[latex size=”3″] v=u+at[/latex]  – Eq 1

And *t gives..

[latex size=”3″]vt = ut+at^{2}[/latex]

Divide both sides by two…

[latex size=”3″]\frac{vt}{2} = \frac{ut}{2} +\frac{ at^{2}}{2} [/latex]

Add ut to both sides, multiply by 2 and tidy up..

[latex size=”3″]s = ut+\frac{ at^{2}}{2} [/latex] – Eq 3

So we now have the four equations of motion for an object which is travelling at a constant velocity or accelerating at a constant rate. As shown you can reason them all out with very simple ideas from first principals. You can also call them whatever number you want as some people label them differently.

So hopfully we have now understood where the formulae comes from and realise that if we drop a ball we must apply the formulae to work out the distance fallen in a more complex way.

Then it gets really interesting when you think about a tanker travelling at a constant velocity which then slows down. How far does it travel as it slows…

[latex size=”3″]s = ut-\frac{ at^{2}}{2} [/latex]

Of course, it will be ut for the whole time and then you take away a little bit of “s” from the other term as you slow.

The Electron a “charged particle”

The story of cathode rays begins in 1855. In that year, Heinrich Geissler invented the mercury vacuum pump. With the pump he could remove almost all of the air from a sealed glass tube.  Geissler’s friend Julius Plucker used the pump to evacuate a special kind of tube. Inside the tube were two electrodes. Plucker attached one electrode, called the anode, to the positive terminal of a battery. He attached the other electrode, the cathode, to the negative terminal. He noticed that the glass near the cathode glowed with greenish light. When Plucker held a magnet near the tube, the glowing spot moved.  Plucker’s student, Johann Wilhelm Hittorf, put solid objects inside the tube between the cathode and the glow. The objects cast shadows. Hittorf concluded that the cathode was emitting something that travelled in straight lines, like light rays. The German physicist Eugen Goldstein named them “cathode rays.”

The English scientist William Crookes thought cathode rays were streams of molecules that had picked up a negative electric charge. Crookes knew from the laws of electricity and magnetism that a charged particle in a magnetic field would move in a circle. Since a magnetic field caused cathode rays to move in a circle, Crookes reasoned, they must be made of charged particles.

If cathode rays were streams of charged particles, an electric field also should have deflected their path. The German physicist Heinrich Hertz tested this hypothesis. He set a cathode ray tube between two metal plates. One plate was positively charged and the other was negatively charged. Negatively charged molecules should have been attracted to the positive plate. When Hertz connected his tube to the battery, the cathode rays kept going in a straight line. Hertz concluded that the cathode rays were a new kind of electromagnetic wave.  Hertz’s student, Philipp Lenard, designed a cathode ray tube with a thin foil at one end. The cathode rays went right through the foil. Since molecules of gas could not go through the foil, Lenard knew that cathode rays could not be charged molecules. He agreed with his teacher that they must be electromagnetic waves.

Then Jean-Baptiste Perrin conducted a very simple but very clever experiment. He accelerated a beam of electrons in a glass tube. You can see at the start of my video how the spot on the glass tube is the impact of the electrons causing fluorescent on paint on the inside of the tube. He then setup a magnetic field at 90 degrees to the beam using coils of wire (Helmholz coils). As you increase the current flow inside the coils the field becomes stronger causing the beam to curve according to Flemings LH rule of FBI. Now as the beam is directed down to a collector which is connected to a gold leaf electroscope the leaf rises. This shows us that the beam is in fact charged. Further experiments show the charge is also negative. This is evidence that cathode rays are in not part of the EM Spectrum.

[hana-flv-player video=”https://www.animatedscience.co.uk/wp-content/uploads/2011/01/charged-electron.flv” width=”400″ height=”330″ description=”Charged Electron” player=”4″ autoload=”true” autoplay=”false” loop=”false” autorewind=”true” /]

Atomic Physics 3D timeline…

Here is a 1st test version of my Atomic Physics software for A-Level students. This one is a rough version to test online which has the following features…

1) Historic rotating time line of the Scientists which did a lot of discoveries in the field of Atomic Physics. You can download images to make a worksheet or your own poster. Also you can copy text from animation. I will be upgrading this soon to have animations / images in the space below the information text which change when you click.

2) A series of video clips in FLV format with menu from Dr Brian Cox about particle physics. I will be upgrading this soon so video player will resize to fill larger area on click.

At the moment it is online only so the fullscreen button does not work. However, I will make an MSI when I have finished it so you can download to your local PC. Any suggestions welcome….

https://www.animatedscience.co.uk/atomic_physics/index.htm

Also if you are a Swish Max 4 Developer here is the SWI file which anyone is free to use for non-profit!  atomic_physics

General GCE Physics Notes…

These are not my own notes but those provided by a very good Physics teacher called Mike Pearce who I used to work with. I am in the process of updating them and integrating them to a more modern form.

They were for quick A-Level revision of any topic and some are a bit deeper than the current A-Level spec. You can get the menu from the link below. They are very good and still great to use.

Please note that within the pages are a pretty old HTML format, so you have to press back on the browser to come back to this page.

 Electricity and Magnetism Heat Oscillations & Waves, Reflection & Refraction Mechanics Solids & Fluids Radioactivity & Quantum Phenomena

New solar fuel machine “mimics plant life”

In the prototype, sunlight heats a ceria cylinder which breaks down water or carbon dioxide

A prototype solar device has been unveiled which mimics plant life, turning the Sun’s energy into fuel.

The machine uses the Sun’s rays and a metal oxide called ceria to break down carbon dioxide or water into fuels which can be stored and transported.

Conventional photovoltaic panels must use the electricity they generate in situ, and cannot deliver power at night.

The prototype, which was devised by researchers in the US and Switzerland, uses a quartz window and cavity to concentrate sunlight into a cylinder lined with cerium oxide, also known as ceria.

Ceria has a natural propensity to exhale oxygen as it heats up and inhale it as it cools down.

If as in the prototype, carbon dioxide and/or water are pumped into the vessel, the ceria will rapidly strip the oxygen from them as it cools, creating hydrogen and/or carbon monoxide.

Hydrogen produced could be used to fuel hydrogen fuel cells in cars, for example, while a combination of hydrogen and carbon monoxide can be used to create “syngas” for fuel.

It is this harnessing of ceria’s properties in the solar reactor which represents the major breakthrough, say the inventors of the device. They also say the metal is readily available, being the most abundant of the “rare-earth” metals.

Methane can be produced using the same machine, they say. Refinements needed  The prototype is grossly inefficient, the fuel created harnessing only between 0.7% and 0.8% of the solar energy taken into the vessel. Most of the energy is lost through heat loss through the reactor’s wall or through the re-radiation of sunlight back through the device’s aperture. But the researchers are confident that efficiency rates of up to 19% can be achieved through better insulation and smaller apertures. Such efficiency rates, they say, could make for a viable commercial device. “The chemistry of the material is really well suited to this process,” says Professor Sossina Haile of the California Institute of Technology (Caltech). “This is the first demonstration of doing the full shebang, running it under (light) photons in a reactor.”

She says the reactor could be used to create transportation fuels or be adopted in large-scale energy plants, where solar-sourced power could be available throughout the day and night. However, she admits the fate of this and other devices in development is tied to whether states adopt a low-carbon policy. “It’s very much tied to policy. If we had a carbon policy, something like this would move forward a lot more quickly,” she told the BBC. It has been suggested that the device mimics plants, which also use carbon dioxide, water and sunlight to create energy as part of the process of photosynthesis. But Professor Haile thinks the analogy is over-simplistic.

“Yes, the reactor takes in sunlight, we take in carbon dioxide and water and we produce a chemical compound, so in the most generic sense there are these similarities, but I think that’s pretty much where the analogy ends.”

The PS10 solar tower plant near Seville, Spain. Mirrors concentrate the sun’s power on to a central tower, driving a steam turbine

Daniel Davies, chief technology officer at the British photovoltaic company Solar Century, said the research was “very exciting”.

“I guess the question is where you locate it – would you put your solar collector on a roof or would it be better off as a big industrial concern in the Sahara and then shipping the liquid fuel?” he said.

Solar technology is moving forward apace but the overriding challenges remain ones of efficiency, economy and storage.

New-generation “solar tower” plants have been built in Spain and the United States which use an array of mirrors to concentrate sunlight onto tower-mounted receivers which drive steam turbines.

A new Spanish project will use molten salts to store heat from the Sun for up to 15 hours, so that the plant could potentially operate through the night.