## SI Units…

Here are some basic SI units that you might want to use in your calculations….

quantitynamesymbolin terms of …
other unitsbase units
frequencyhertzHz s−1
forcenewtonN m kg s−2
pressure, stresspascalPaN/m2m−1 kg s−2
energy, work, heatjouleJN mm2 kg s−2
power, heat flowwattWJ/sm2 kg s−3
electric chargecoulombC s A
electric potentialvoltVW/Am2 kg s−3 A−1
resistanceohmΩV/Am2 kg s−3 A−2
conductancesiemensSA/Vm−2 kg−1 s3 A2
magnetic fluxweberWbV sm2 kg s−2 A−1
magnetic flux densityteslaTWb/m2kg s−2 A−1
inductancehenryHWb/A m2 kg s−2 A−2
celsius temperaturedegree celsius K
luminous fluxlumenlmcd srm2 m−2 cd
illuminanceluxlxlm/m2m−2 cd
absorbed dosegrayGyJ/kgm2 s−2
equivalent dosesievertSvJ/kgm2 s−2
catalytic activitykatalkat s−1 mol

## Unit 1 AS Exam Past Papers

If you need the 2009-2011 Papers here they are…

Unit 1 Exam Papers

## Why do thick wires have lower resistance?

This text has come from Furry Elephant so I don’t take credit but it is cool, read and have a think…
Even the most apparently reputable sources of information are sometimes full of misconceptions. The BBC manages to demonstrate several all at the same time with this terrible animation trying to explain why thicker wires have a lower resistance than thin ones.
The main argument is that a thick wire has ’more space’ for the electrons to move around in than a thin wire. But wires are made from atoms – that’s where the free electrons come from. So thicker wires have more atoms and so no more empty space (per cross-sectional area) than thin ones. Another implication of the animation is that the wires are like empty tubes. This suggests that the electrons come from the battery as a sort of source rather than already being there everywhere in the circuit. The final problem is the speed of the electrons. Since the animation shows a longer path for the electrons in the empty thick wire their speed must have increased. In fact, the opposite is the case. Electrons travel slower in thick wires.

For a copper wire (at a given temperature) the speed of the electrons depends only on the voltage across it. Imagine a three-lane road and a single-lane road with cars all going at the same speed. More cars pass per second in the wider road even though the speed is the same. More cars (charges) per second means higher current for a given voltage and so smaller resistance.

Since current is the same around a simple series circuit the charges have to go faster where the wire is thinner. Faster charges mean more interactions with the ionic lattice per second and so higher resistance.

## Exam Past Papers Unit 5 & 5D

Here is a zipped file structure to download to your PC. It contains all the exam questions from AQA for Unit 5 from 2002 to 2010. Remember this includes the legacy or old spec papers from 2002-8 which are very similar.

Turning Points Exam Papers 2002_10

## My Paintings

Here are three examples of my own paintings as the first post in this area..

Spain – This is a thickly based acrylic painting which took an age to dry. It is currently in Spain as a gift to a Spanish friend of mine when he got married. It was designed to capture the vivid colour of spain with a Salvador Dali / Henri- Matisse twist.

Animal – This painting started off an a computer generated image in MS Paint on Windows 3.1. I liked it so much I painted it on board in primary acrylic colours. It is now my logo for the website and Animated Science!

Reflections – This painting was inspired by my techincal drawing lessons. I wanted to look at the idea of a refection of a shape which is subdivided. I used a board which my art teacher gave me which curved a lot in the end!

## Beginners Guide to Sausage Making..

Hi,

This PDF is not mine but from https://www.forum.sausagemaking.org and is really cool. If you are starting out then check it out, also some good ideas for mixtures.

SausageMaking

## Cross Winds Calculations..

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