What is electrical charge? Essential Questions What is electrical charge? How can electrical charge build up (static electricity)? How can electrical conductivity be explained using the particle model?

Electric Charge All atoms are made up of just 3 different types of subatomic particles sub – means ‘under’ or smaller than - ELECTRONS are very light and have a NEGATIVE charge + PROTONS are much heavier and have a POSITIVE charge NEUTRONS are as heavy as protons but have NO charge (they are neutral)

- - - - + + + - - Electric Charge Different types of atom are known as elements, they have different numbers of protons, neutrons and electrons Name Hydrogen Helium Lithium Protons 1 2 3 Neutrons 4 Electrons - - - - + + + NUCLEUS Centre of the atom, contains protons and neutrons - -

Electric Charge If a substance has more positive charges than negative charges it has a positive charge overall + + - + + - + If a substance has more negative charges than positive charges it has a negative charge overall + - - - - + - + -

Static Electricity Electrons can transfer from one substance to another. For example if you rub a balloon with a cloth, some electrons transfer from the cloth to the balloon - + + - - + - + + -

Static Electricity Electrons can transfer from one substance to another. For example if you rub a balloon with a cloth, some electrons transfer from the cloth to the balloon - + - + + - - - - - + - + - -

Static Electricity Electrons can transfer from one substance to another. For example if you rub a balloon with a cloth, some electrons transfer from the cloth to the balloon - + + - - - - - - + + - + - - The balloon is now negatively charged The cloth is now positively charged

Static Electricity If the charge is unable to move we call this STATIC ELECTRICITY. (Static means standing still or not moving) - + + - - - - - - + + - + - - The balloon is now negatively charged The cloth is now positively charged

Experiment – charge transfer 1. Rub a rod with the cloth to transfer electrons and build up a static charge on the rod. 2. Turn on a tap so that there is a very gentle but constant trickle 3. Hold the rod close to the water (do not touch it). Observe what happens

- - - - - - - - - - Explanation + - - + + - + + - - + - Water has a partial positive charge on the Hydrogen atoms + - - + - + - - - - and a partial negative charge on the oxygen + - - + - - - The positive side of the water is attracted towards the negative charge on the rod - - + - -

Electric Current Solid substances are made up of billions upon billions upon billions of atoms held together in a tight lattice

Electric Current Some substances can let their outermost electrons move around the other atoms – we refer to these substances as METALS - - - - - + - + + - - -

Electric Current Some substances can let their outermost electrons move around the other atoms – these are called METALS

Conductors and Insulators Substances which allow electric charge to move are known as CONDUCTORS Because all METALS allow their outer electrons to move they are all CONDUCTORS If a substance does not allow electric charge to move it is known as an INSULATOR Substances like plastic, wood or rubber are INSULATORS

Electric Current Adding a battery creates a ‘potential difference’ all the electrons flow in the same direction (away form the ‘-’ towards the ‘+’ The battery pushes electrons in to the conductor at the ‘-’ end - +

! ? What sort of material would be used in electrical wiring? Think, Pair, Share ? ! What sort of material would be used in electrical wiring? Why does electrical wiring have plastic on the outside?

Summary What is electrical charge? electrons have a negative (-) charge protons have a positive (+) charge substances with more electrons than protons are negatively (-) charged substances with more protons than electrons are positively (+) charged How can electrical charge build up (static electricity)? electrons can be transferred from one substance to another if the substance is an insulator, charge can build up on it when it finds a path (conductor) to follow it will flow down it How can electrical conductivity be explained using the particle model? in solids, atoms are arranged in a lattice structure in conductors, the outer electrons are free to move between the particles when a potential (voltage) is applied the electrons flow from the negative end towards the positive end