Student Notes Unit P2: Physics for your future Topic 1: Static and current electricity

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.1 Describe the structure of the atom, limited to the position, mass and charge of protons, neutrons and electrons

Particle ProtonNeutronElectron Relative charge+10 (neutral) Relative mass (negligible) PositionNucleus Shell Protons and neutrons are found in the nucleus of an atom Electrons move around the nucleus of an atom in energy shells All atoms are made up of electrons, protons and neutrons

Atomic number The atomic number tells you the number of protons in the nucleus. Atoms always the same number of electrons as protons. Mass number The mass number is the total number of protons and neutrons. F 19 9 Atomic number Mass number 9 protons (9+) 9 electrons (9-) 10 neutrons (0 charge) Example

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.2 Explain how an insulator can be charged by friction, through the transfer of electrons 1.3 Explain how the material gaining electrons becomes negatively charged and the material losing electrons is left with an equal positive charge 1.4 Recall that like charges repel and unlike charges attract 1.5 Demonstrate an understanding of common electrostatic phenomena in terms of movement of electrons, including: a shocks from everyday objects b lightning c attraction by induction such as a charged balloon attracted to a wall and a charged comb picking up small pieces of paper Only underlined parts from 1.5 are covered in this lesson

… from the cloth to the balloon Static electricity is caused by friction when you rub insulators together Electrons transferred (negative charge) …. e-e- e-e-

Two different rods will attract each other if they have different charges. Two rods made of the same material will repel each other due to having the same charge. Attraction and repulsion

Electrostatic Induction When a charged object moves near to an uncharged object, a charge is induced on the uncharged object due to the electrostatic field around the charged object. This is electrostatic induction - the creation of a charge by the influence of a nearby charged object, not by actual contact. (Here, induction means to influence without contact).

How? Electrostatic Induction

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.6 Explain how earthing removes excess charge by movement of electrons 1.5 Demonstrate an understanding of common electrostatic phenomena in terms of movement of electrons, including: a shocks from everyday objects b lightning c attraction by induction such as a charged balloon attracted to a wall and a charged comb picking up small pieces of paper Only underlined parts from 1.5 are covered in this lesson

Static electricity can build up on clouds and can cause a huge spark to form between the cloud and the ground. The lightning we see is caused by charged particles flowing through the atmosphere. Lightning

Lighting rods are found on tall buildings. If lightning hits the lighting rod the electric current flows safely to Earth down a thick copper wire which is connected to a metal block in the ground

A potential difference is created between the dome and the conducting sphere Dome Conducting sphere Negative charge on the dome induces a charge on the conducting sphere Negative charge builds up on the dome Charge jumps from the dome to the conducting sphere and then discharges (flows) to earth earth

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.7 Explain some of the uses of electrostatic charges in everyday situations, including paint and insecticide sprayers 1.8 Demonstrate an understanding of some of the dangers of electrostatic charges in everyday situations, including fuelling aircraft and tankers together with the use of earthing to prevent the build-up of charge and danger arising

+ Advantages of electrostatic spraying: Spray spreads out more evenly Spray gets attracted to the object (reduces waste/saving money) The positively charged spray is attracted to oppositely/negative charged object Spray is given a charge as it leaves the nozzle Negatively charged object - Electrostatic spraying

The charge of the spray and the object being sprayed can be the other way around – same explanation! Electrostatic spraying

insecticide sprayers Electrostatic paint spraying

Dangers with fuelling aircraft As an aircraft flies through the air, it can accumulate a charge of static electricity. If the aeroplane is not earthed before fuelling, an electric spark can occur which may ignite fuel vapours. Also the moving fuel rubs along the inside of the fuel pipe. The friction causes the pipe to get charged up as it picks up electrons from the fuel. The pipe gets a negative charge that could lead to a spark. So the pipe, the truck and the aeroplane are all earthed. As long as the aircraft is earthed to the fueling apparatus the charge can flow safely away.

Static electricity can be dangerous! A spark could ignite a flammable gas or liquid.

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.9 Recall that an electric current is the rate of flow of charge 1.10 Recall that the current in metals is a flow of electrons 1.11 Use the equation: charge (coulomb, C) = current (ampere, A) x time (second, s) Q = I x t

You need around electrons to have a charge of 1 coulomb! Charge of 1 electron = Coulombs Charge of 1 electron = 1.6 x Coulombs Electrons are negatively charged particles We measure the amount of charge something has in coulombs (C)

What is current? Current is the rate of flow of electric charge around a circuit. e e e e e e e e e e e 1 Amp = 1 Coulomb of charge flowing past a point 1 second 1 A = 1 C s

Q I t Charge = current x time Q = I x t (coulomb, C) (ampere, A) (second, s)

W e A re L earning T o Unit P2: Physics for your future Topic 1 Static and current electricity 1.12 Recall that cells and batteries supply direct current (d.c.) 1.13 Demonstrate an understanding that direct current (d.c.) is movement of charge in one direction only

DC (direct current) is current that is always flowing in one direction. Sources of DC? Cells or batteries + - The voltage of the cell pushes and pulls the electrons around the wire