OpenLLM-France/wikimedia huggingface dataset:
# A-level Physics (Advancing Physics)/Generators/Worked Solutions

1. Draw diagrams of an alternating current, the 'direct current' produced by a DC generator, and this current once it has been smoothed with a capacitor.
2. What is the phase difference (in radians) between the voltages produced by a three-phase generator?
${\frac {2\pi }{3}}^{c}$
3. According to Faraday's law, what three things will increase the amplitude of the emf created by a generator?
$\epsilon =-{\frac {dN\phi }{dt}}$
So, more coils, a stronger magnetic field or a higher frequency of rotation will increase the amplitude of the emf.
4. If an albatross touched two power cables carrying AC in phase, what would happen?
Nothing - there is no potential difference between the two cables.
5. What would happen if the two cables carried three-phase power?
Unfortunately, dead albatross - there is potential difference between the two cables.
# A-level Physics (Advancing Physics)/Gravitational Fields

The gravitational field, or gravitational field strength is the force exerted by gravity on an object per. unit mass of the object:
$g={\frac {F_{grav}}{m}}$
As gravitational field strength is a measure of the force exerted on each unit of mass, its unit is Nkg$^{−1}$. If we consider a planet, Body A, the gravitational field strength experienced by another object, Body B, is given by:
$g={\frac {\frac {-GMm}{r^{2}}}{m}}={\frac {-GM}{r^{2}}}$
Dimensions :- $[g]=[G]{\frac {[M]}{{[r]}^{2}}}=[G]ML^{-2}=LT^{-2}$
This is the total force exerted on Body B divided by the mass of Body B. Inside the planet, force is proportional to the distance from the centre, so the field is also proportional to distance.

## Acceleration

Force is given by:
$F=ma$
This means that:
$g={\frac {ma}{m}}=a$
This shows that the gravitational field strength is also the acceleration due to gravity on any object. This acceleration is the same for any object, regardless of mass. When considering small heights above the Earth's surface, such as those in our day-to-day experiences, g remains roughly constant.

## Field Lines

The gravitational field can be represented using field lines. These run in the direction that a mass would be accelerated in initially. The object will not necessarily fall along the field lines, but the acceleration will always be in the direction of the field lines. The closer the field lines are together, the denser the gravitational field.

## Questions

G = 6.67 x 10$^{−11}$ m$^3$kg$^{−1}$s$^{−2}$
1. A 15 kg object has a weight of 8000N. What is the gravitational field strength at this point?
2. Draw a graph of gravitational field strength against distance.
3. What is the gravitational field strength of the Sun (mass 2 x 10$^{30}$kg) on the Earth (mass 6 x 10$^{24}$kg, mean orbital radius 15 x 10$^{10}$m)?
4. What is the difference in the acceleration due to gravity over a vertical distance d?
5. How far would one have to travel upwards from the Earth's surface to notice a 1Nkg$^{−1}$ difference in gravitational field? (The Earth has a radius of 6400 km.)
Worked Solutions
# A-level Physics (Advancing Physics)/Graphs/Worked Solutions

1. In the following distance-time graph, what is the velocity 4 seconds after the beginning of the object's journey?
At this point, the graph is a straight line. So:
$v={\frac {ds}{dt}}={\frac {10-0}{6-0}}={\frac {5}{3}}\approx 1.67{\mbox{ms}}^{-1}$
2. What is the velocity at 12 seconds?
Approximately, there is a rough straight line at this point. The object is travelling towards home 2 ms$^{−1}$ each second (look at the previous second, for example). So, its velocity is -2 ms$^{−1}$.
3. In the following velocity-time graph, how far does the object travel between 7 and 9 seconds?
Distance travelled is equal to the area under the graph. Between 7 and 9 seconds, this is the shaded area of the graph. So, calculate the area of the triangle:
$A={\frac {bh}{2}}={\frac {2\times 3}{2}}=3{\mbox{m}}$
4. What is the object's acceleration at 8 seconds?
There is a straight line between 7 and 9 seconds which we can use to answer this question. The acceleration is equal to the gradient of the graph, so:
$a={\frac {3}{2}}=1.5{\mbox{ms}}^{-2}$
5. A car travels at 10ms$^{−1}$ for 5 minutes in a straight line, and then returns to its original location over the next 4 minutes, travelling at a constant velocity. Draw a distance-time graph showing the distance the car has travelled from its original location.
10ms$^{−1}$ = 600 metres / minute.
6. Draw the velocity-time graph for the above situation.
The velocity from 0-5s is 10ms$^{−1}$. The velocity from 5-9s is:
$v={\frac {3\times 10^{3}}{4}}=750{\mbox{ metres/minute}}=12.5{\mbox{ms}}^{-1}$
7. The velocity of a ball is related to the time since it was thrown by the equation $v=30-9.8t\,$. How far has the ball travelled after 2 seconds?
$s=\int _{t_{1}}^{t_{2}}f(t)\,dt=\int _{0}^{2}30-9.8t\,dt=[30t-4.9t^{2}]_{0}^{2}=30(2)-4.9(2^{2})-30(0)+4.9(0^{2})=60-19.6=40.4{\mbox{ m}}$
# A-level Physics (Advancing Physics)/Gravitational Fields/Worked Solutions

G = 6.67 x 10$^{−11}$ m$^3$kg$^{−1}$s$^{−2}$
1. A 15 kg object has a weight of 8000N. What is the gravitational field strength at this point?
$g={\frac {F_{grav}}{m}}={\frac {8000}{15}}=533{\mbox{ Nkg}}^{-1}$
2. Draw a graph of gravitational field strength against distance.
Since gravitational field strength is proportional to gravitational force, the two graphs look very similar.
3. What is the gravitational field strength of the Sun (mass 2 x 10$^{30}$kg) on the Earth (mass 6 x 10$^{24}$kg, mean orbital radius 15 x 10$^{10}$m)?
$g={\frac {GM}{r^{2}}}={\frac {6.67\times 10^{-11}\times 2\times 10^{30}}{(15\times 10^{10})^{2}}}=5.93{\mbox{ mNkg}}^{-1}$
4. What is the difference in the acceleration due to gravity over a vertical distance d?
$\Delta g={\frac {GM}{(r+d)^{2}}}-{\frac {GM}{r^{2}}}=GM\left({\frac {1}{(r+d)^{2}}}-{\frac {1}{r^{2}}}\right)={\frac {GM(r^{2}-(r+d)^{2})}{r^{2}(r+d)^{2}}}={\frac {GM(r^{2}-r^{2}-2rd-d^{2})}{r^{2}(r+d)^{2}}}={\frac {-GMd(2r+d)}{r^{2}(r+d)^{2}}}$
5. How far would one have to travel upwards from the Earth's surface to notice a 1Nkg$^{−1}$ difference in gravitational field? (The Earth has a radius of 6400 km.)
$1={\frac {GMd(2r+d)}{r^{2}(r+d)^{2}}}$
$GMd(2r+d)=r^{2}(r+d)^{2}$
$2GMrd+GMd^{2}=r^{2}(r^{2}+2rd+d^{2})=r^{4}+2r^{3}d+r^{2}d^{2}$
$d^{2}(r^{2}-GM)+dr(2r^{2}-2GM)+r^{4}=0$
Using the quadratic formula:
$d={\frac {2GMr-2r^{3}\pm {\sqrt {r^{2}(2r^{2}-2GM)^{2}-4r^{4}(r^{2}-GM)}}}{2(r^{2}-GM)}}={\frac {2GMr-2r^{3}\pm {\sqrt {4r^{6}-8GMr^{4}+4G^{2}M^{2}r^{2}-4r^{6}+4GMr^{4}}}}{2(r^{2}-GM)}}$
$={\frac {2GMr-2r^{3}\pm r{\sqrt {4r^{4}-8GMr^{2}+4G^{2}M^{2}-4r^{4}+4GMr^{2}}}}{2(r^{2}-GM)}}$
Which is very horrible. If you plug in the numbers, you get:
$d={\frac {4.598272\times 10^{2}1\pm 4.853341552\times 10^{21}}{-7.1848\times 10^{14}}}$
Since we want a negative d (because of the minus sign we ignored right at the beginning):
$d={\frac {4.598272\times 10^{2}1+4.853341552\times 10^{21}}{-7.1848\times 10^{14}}}=-13155{\mbox{ km}}$
Although, I have to confess, there was so much scope for error that it is almost certain that this is the wrong answer. If you fancy wading through and checking, feel free!
[*] Solution :
g'=g-1=9.8-1=8.8N/kg g=GM/(R+d)^2 => $(R+d)^{2}=GM/g'=>R+d=sqrt(GM/g')=>d=sqrt(GM/g')-R$
d=349.96 km
--Sjlegg (talk) 14:18, 23 April 2009 (UTC)
# A-level Applied Science/Physics of Performance Effects
## About this Unit

From the AQA Specification:
   You need to produce a portfolio of evidence which considers how light and sound can be used in a performance and the science behind the design of a lighting and sound system in a performance you attended.
   Your portfolio of evidence should comprise:
   A. a design for a sound system and appropriate control system for a venue you have chosen.
   B. a design for a lighting set-up and control system for a performance, or part of a performance, of your choice.
   C. a description and evaluation of a sound and lighting system used
   in a performance you have attended.

## How you will be assessed

This unit is assessed through the work you complete for your portfolio.
The marking criteria are found in the AQA specification.

## What you need to know

The nature of sound and its application to sound systems.
Sound control systems
The nature of light and its application to lighting systems
Lighting control systems
Evaluating a performance
# A-level Applied Science/Investigating Science at Work/Types of science organisation

Applied science is the application of knowledge from one or more scientific fields to practical problems. Many applied sciences can be considered forms of engineering. Applied science is important for technology development.
Academic disciplines that may be considered to be applied sciences include agriculture, architecture, education, engineering, ergonomics, design, family and consumer science, forestry, forensics, health sciences, library and information science, medicine and military science. There are also applied branches of most other sciences.
Instrumental science, an applied science, is a systematic way of solving problems. It is not a science of discovery but rather deals with manipulation to solve a particular problem such as "The crops are dying. We need to find a way to stop this." Instrumental sciences are well known for research and development which result in new technology.
In researching local science-based businesses, include firms which are involved in:
(1) Producing:
* products from plants, animals or microbes;
* water, gas, oil, gravel, clay, stone or minerals;
* chemicals, paints, dyes, fertilisers and plastics;
* pharmaceuticals, for example medicines;
* mechanical or electrical devices;
* refined fuels;
* processed and packaged products.
(2) Providing services:
* health;
* conservation and use of the environment;
* monitoring the environment;
* animal welfare;
* analysis;
* communication;
* education in science and technology;
* distributing and selling food and other products;
* distributing energy resources.
# A-level Applied Science/Investigating Science at Work/How science is used

You need to consider the main scientific processes in one chosen industry. Remember also to write about the supporting processes e.g. waste & pollution management, quality checks, etc.
# A-level Applied Science/Investigating Science at Work
## About this Unit

From the AQA Specification:
   You need to produce a portfolio of evidence to show how science is used to provide products and services in different kinds of science based organisations.

## How you will be assessed

This unit is assessed through the work you complete for your portfolio.
The marking criteria are found in the AQA Specification.

## What you need to know

The types of organisation which use science.
How science is used in organisations.
How health and safety regulations are used in the workplace.
How the organisation impacts on the local community.

## Resources

The specification requires you to identify and use appropriate research methods to complete your portfolio. It will not be possible, therefore, for this textbook to give extensive details on any of the sections your portfolio needs. Below are some suggestions and links you might find useful:
Research methods.
Health and safety regulations.
INCO case study.
GlaxoSmithKline site for applied science - how science is used in the pharmaceutical industry.
# A-level Applied Science/Investigating Science at Work/Local community impact

How the organization impacts on the local community
You should consider the socio-economic and environmental effects(beneficial and detrimental) of your chosen organization, and how it impacts on the local community. You should identify:
* The ways in which energy consumption is managed in the organization;
* The demands made on transport and communication systems;
* Management of waste materials and the effect this may have on the local environment;
* Contributions to the local economy. These could include community use of facilities, sponsorship of local groups etc.
# A-level Applied Science/Investigating Science at Work/Resources
## Research

Using this internet-based textbook, it is easy to forget about other sources of information.
* Books (including telephone directories).
* Personal contact (phone, letter, e-mail).
* Local knowledge.
* Friends and family.
* Journals and newspapers.
* Careers advisors.
* Advertising.
* ThomsonLocal.com
* yell.com

## Health and safety regulations

Health & Safety Executive (HSE).

## INCO

Main INCO website.
Wikipedia article on INCO.
Mond nickel-refining process.
Data on nickel carbonyl.
2004 environmental report.
2004 social responsibility report.
2003 Summary of Clydach production facilities.
2002 Speech by Scott Hand, Deputy Chairman and Chief Executive Officer.
# A-level Applied Science/Physics of Performance Effects/Evaluating a performance

* Describe the lighting set-up.
* Calculate the cost of lighting the performance.
# A-level Applied Science/Finding out about substances/Qualitative

The basic question addressed by qualitative analysis is: Is there any X in the sample?
In contrast, quantitative analysis answers the question: How much X is there in the sample?
In practice, qualitative analysis records if the amount of X is above a certain threshold value.

# Uses of qualitative analysis

Reagent
Effects
6M HCl
Increases [H+]
6M HNO3
Increases [H+]
6 M NaOH
Increases [OH-]
6M NH3
Increases [NH3]

## Limitations

Group I: Ag+, Hg22+, Pb2+
Group II: Bi3+, Cd2+, Cu2+, Hg2+, (Pb2+), Sb3+ and Sb5+, Sn2+ and Sn4+
Group III: Al3+, (Cd2+), Co2+, Cr3+, Fe2+ and Fe3+, Mn2+, Ni2+, Zn2+
Group IV: Ba2+, Ca2+, K+, Mg2+, Na+, NH4+
Many reagents are used in qualitative analysis, but only a few are involved in nearly every group procedure. The four most commonly used reagents are 6M HCl, 6M HNO3, 6M NaOH, 6M NH3. Understanding the uses of the reagents is helpful when planning an analysis.

# Standard procedures
## Analysis of mine water sample
### A. Cations

* To a 2 cm³ mine water sample: Add sodium hydroxide solution dropwise until it is in excess.
* Filter the mixture from (1) and add sulphuric acid dropwise to the filtrate.
* Add aqueous ammonia solution to the acidified filtrate from (2).
* To a 2 cm³ mine water sample: Add aqueous ammonia solution dropwise until it is in excess.
* Filter the mixture from (4) and add sulphuric acid dropwise to the filtrate.
* To a drop of mine water sample: Add a drop of potassium thiocyanate solution.
* To a drop of mine water sample: Add a drop of potassium hexacyanoferrate (III) solution.
* Flame test the mine water sample.

### B. Anions

* Test the pH of the mine water sample. What anions would react to form gases at this pH?
* To a drop of mine water sample: Add a drop of barium nitrate solution.
* To a drop of mine water sample: Add a drop of silver nitrate solution.
* To a 1 cm³ mine water sample: Add powdered Al and aqueous NaOH – if a reaction occurs test gas with damp red litmus paper.

### Questions

* Which ions have you identified as being present?
* Which ions are definitely not present?
* Are there any ions which you are unsure about?
* Write a report of this practical work. Discuss the limitations of qualitative analysis. Give a full account of all your experiments and observations.
# A-level Computing 2009/AQA/C Sharp

C# is a popular language

## C# Myths

C# is now Microsoft Language of choice if you work on thick client (desktop applications) or Silverlight (their rich web solution).
The language has similar syntax to Java and has similar core class libraries supplied, Streams for an example. This allows developers to easily work on either platform. The language has addition constructs for Properties, over and above Java.
The MVVM design pattern is extensively supported by C# , which allows clear separation between UI and Business Logic for thick client (desktop) and Silverlight (web). Which also allows code to be re-used between desktop and Silverlight. This allows a declaration of UI controls to be cleanly bound to business data. This enables a graphics designer to work alongside/parallel to a developer of business logic.
C# is strongly typed/type safe, and thereby avoids common programming errors and reduces debug time as issues are resolved at compile time. This also allows C# to run in a sandbox.
The use of { and } to scope code blocks provides a very clean and simple visual display of code.
C# uses the CLR to perform automatic memory management with garbage collection and therefore does not have the memory management problems associated with C/C++.
An Embedded version of C# exists, but the processor will require considerable memory (relative to a typical embedded system) to support the CLR.
Underlying Windows libraries can be called if they are already not supported by the .NET library.

## Why not C#?
## Online resources

Microsoft .NET Framework Application Development Foundation (70-536). Although now a old book is a good starting place for somebody starting out, as it writes the basics of file I/O (Streams), Exceptions, Regular Expressions, Collections, Graphics, Threading, Logging and Systems Management.
# A-level Computing 2009/AQA/Advanced Systems Development/Databases

Database Concepts
Traditional File Approach
Most organisations began information processing on a small scale, buying a computer for perhaps one or two individual applications, and then computerising other departments one by one. Applications were developed independently, and files of information relevant to one particular department were created and processed by dozens or even hundreds of separate programs. This led to several problems such as:
Data redundancy - The same data was duplicated in many different files.
Data inconsistency - When the same items of data were held in several different file, the data has to be updated in each separate file when it changes.
# A-level Computing 2009/AQA/Computer Components, The Stored Program Concept and the Internet/Consequences of Uses of Computing

* Legal and Ethical Issues
* Discuss issues of ownership of information and programs, and the protection of data.
* Consider current legal controls which specifically refer to computerised data and programs, and the implications of current legislation (see the Resource Bank).
* Hacking.
* Consider how digital rights can be managed.
* Code of Conduct.
* Economic and Social Issues Discuss the social consequences of current uses of computing.
* Be aware of emerging technologies and appreciate their potential impact on society.
* Robotics:
* What are machines good and bad at, in comparison to humans?
* What can this tell us about the way that the human mind works?
* What can we learn from machines?
* What are the limitations of using machines as tools?
* Robotics
* Emerging technologies
# A-level Computing 2009/AQA/2015 ALevel Paper 1/Fundamentals of programming

* C#
* Java
* Pascal/Delphi
* Python
* VB.Net
# A-level Computing 2009/AQA/Advanced Systems Development

* Applications and Effects
* Databases
* Systems Development
* Hardware Devices
* Networking
# A-level Computing 2009/AQA/Computer Components, The Stored Program Concept and the Internet

This exam is worth 40% of your AS grade (20% of A2). It is examined in June.

## Definitions

Unit 2 definition list

## Past Papers

http://www.aqa.org.uk/subjects/ict-and-computer-science/a-level/computing-2510/past-papers-and-mark-schemes
# A-level Computing 2009/AQA/Advanced Systems Development/Hardware Devices

1.1 Computer Hardware 1.1.1 Computer Concepts A very basic model of a computer would be:
The refined diagram shows the basic components of a computer system.
RAM Random Access Memeory. Stores loaded programs and data to be processed. There are two types: volatile and non-volatile. Unlike non-volatile memory, volatile memory is lost when the computer is switched off or reset.
ROM Read Only Memory. Stores information about BIOS and startup routines.
1.1.2 Measuring Storage Both the primary and auxiliary devices have capacity measured in bits, bytes, kilobytes, megabytes and gigabytes.
A 1 or a 0 is a BInary digiT (Bit).
There are 8 bits in a byte 1024 bytes in a kilobyte 1024 kilobytes in a megabyte 1024 megabytes in a gigabyte Therefore there are 1,048,576 bytes in a megabyte.
A double density floppy disk holds 720Kb of data. A high density floppy disk contains about 1.44Mb of data.
Many computers store one character as one byte.
1.1.3 Computer Categories System Description
Microcomputers: This a computer which uses a microprocessor as its CPU. Includes PCs, laptops etc. They typically have between 1 and 128Mb of memory (RAM). They process data in anything from 8-bit ro 64-bit chunks.
Minicomputers: These are systems designed for multi-user access several terminals. Varies from processing power from a very powerful micro to a small mainframe.
Mainframes: Supports hundreds of terminals for multi-user access. Large amount of primary and auxiliary storage.
Supercomputers: These are the fastest and most expensive systems. Although they are not multi-user machines, they are used when a vast amount of processing is to be done.
1.1.4 Computer Configuration This term describes the collection of hardware in use. A large computer configuration would consist of several hundred micros in a building linked together by cabling to form a local area network (LAN).
1.1.5 Embedded Systems An embedded system is dedicated to one specific task. They are special purpose systems.
Embedded systems typically have their programs stored in ROM as opposed to auxiliary storage and RAM. These programs are referred to as firmware - a combination of software and hardware.
# A-level Computing 2009/AQA/Computer Components, The Stored Program Concept and the Internet/Consequences of Uses of Computing/Legal and ethical issues

With the growth of Information Technology a host of legal and ethical issues have arisen. These range from the laws that protect the work people create using computers, to the ethical and legal problems brought about by the use of robots in modern warfare.
# Advanced Interactive Media/Other Topics/The Visual Story Network

The Visual Story Network had a conference September 16 through September 18. The gathering was made up of influential Christian media creators and missionaries who came for encouragement and inspiration for the soul purpose of uniting together.
The Visual Story Network is a coalition of missional and creative Christians working together to fuel a global movement of visual story for the kingdom of God. We live in a transitional time in the history of the Church. We believe a great opportunity exists to move beyond preach and print to portray. When God’s people consistently create and share visual stories in culturally compelling ways with every person on the earth so people can experience life-change through Jesus a movement will have occurred. We define visual story as combining narrative and visual media in communicating the message of Christ and His kingdom.
# Advanced Interactive Media/Post Discussions From Facebook Here That Don't Fit Under Existing Chapter Titles

Student's written responses on the last exam that are worth thinking about:
Below are comments from thoughtful people in response to Podcast topics that can be found at Don Eland's Podcast site: http://web.archive.org/20100703122442/web.mac.com/elandinteractive/iWeb/elandinteractive/Podcast/Podcast.html
Titles for Podcasts:
"Income and education are driving the technology revolution, not youth culture as is assumed by most people"