AQA GCSE Physics: Unit 2 Electricity Section
Useful Information • AQA Specification can be found by clicking this link. http://store.aqa.org.uk/sciencelab/AQA-PHYS-W-SP.PDF • GCSE Bitesize relevant pages (Electricity section)http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/electricity/ • S-cool physics current electricity section. http://www.s-cool.co.uk/gcse/physics/static-and-current-electricity
When certain insulating materials are rubbed against each other they become electrically charged. • Negatively charged electrons are rubbed off one material onto the other.
The material that gains electrons becomes negatively charged. • The material that loses electrons is left with an equal positive charge. • Have a look at these excellent simulations from the University of Colorado. • Balloons and Electricity http://phet.colorado.edu/en/simulation/balloons • John Travoltage http://phet.colorado.edu/en/simulation/travoltage
Dangers of Static • Can you think of any dangers of static electricity?
Uses • Can you think of any uses of static electricity? • Some ideas here: http://en.wikibooks.org/wiki/GCSE_Science/Uses_of_static_electricity
Conductors • In conductors such as metals electrical charges can move easily. This is because they have a sea of free electrons.
The Coulomb • The charge on an electrons is very very small. • It is useful to think of electrons moving around in groups called Coulombs. • We talk about a Coulomb of charge.
Voltage –see later for a fuller explanation • Fancy name – Potential difference • When a coulomb of charge moves around a circuit energy is transferred. • The amount of energy transferred per Coulomb is called the voltage. • Voltage = Energy/Charge
Electrical Symbols • Do you know the symbols for the following electrical components?
Resistance • It is easier to pass current through some components than others. • We say that the opposition provided by a component to the current flowing through it is called its resistance. • The greater the resistance then the smaller the current for a given potential difference.
Define Ohm’s Law • Ohms Law is to do with the relationship between voltage and current. It also is to do with temperature. • You need to be able to write down the law.
Electrical Current • Electrical Current is a flow of electric charge. • In metals these charges are electrons. • The size of the electric current is the rate of flow of electric charge.
Can you do these questions? • A current of 2 A flows through an electric light bulb. How much charge flows through the bulb in two minutes? • A charge of 100 Coulombs flow through a component for 20 seconds. What current flows through the component?
Work out the resistance of each of the colour coded resistors
Current – Potential Difference Graphs – metal wire at constant temperature
You can learn about circuits easily by simulating them. • Download this simulator from the University of Colorado and have a go. http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc
If the potential difference of the cell is 60 V then what is the current flowing through all three resistors?
Calculate the current in the two resistors and the total current
It can be more complicated if the cells are not all connected in the same direction
Make sure you learn these facts about LED’s • An LED emits light when a current flows through it in the forward direction. • There is an increasing use of LEDs for lighting, as they use a much smaller current than other forms of lighting.
LDR’s • Light Dependent Resistors • What are they used for?
What is the relationship between resistance and temperature?
Learn this about a thermistor • The resistance of a thermistor decreases as the temperature increases. • A thermistor that does is said to have a _________ _________ __________.
AC and DC • What does AC and DC stand for and what do they mean? • Have a listed to AC/DC from starlight express. Click for the Youtube video: http://www.youtube.com/watch?v=c8OX7H1mJpw