physics - yr 9

Electricity

• electricity is the movement of energy through charged particles, like electrons or ions

• charged particles have a property called electric charge, which means they can attract or repel other charged particles

• electric charge comes in two types: positive or negative

electrons

• electrons are the charges particle most commonly involved in electricity

• in most materials, electrons are tightly bound to their atoms, however, in electrical conductors, they are able to freely move between atoms

• materials in which electrons are held on loosely and flow freely between atoms are called electrical conductors

• some atoms hold onto their electrons tightly and electrons do not move through these materials very well

• these materials are called insulators

• conductors are conductors because their electrons are loosely bound

• insulators are insulators because their electrons are very tightly bound

• there are 2 main ways electricity can work, depending on what the electrons are doing

  1. static electricity: happens when electrons build up in one place and don’t move (static means not moving)

  2. current electricity: happens when electrons are able to move through a pathway. in some circuits, they move in one directions, and in others, they switch directions back and forth

anything that is polar has an intrinsic charge

Requirements for static electricity

1. for static electricity to occur the 2 materials need to be in contact (ideally rubbing hard)

2. In the rubbing of the materials, there should be an electrical charge imbalance

static electricity

• some insulating (non-conducting) materials can “steal“ electrons from other materials when rubbed together

• the object that gains electrons now has a negative change

• the object that loses electrons now has a positive charge

• static electricity is a build up of electric charge on a surface

• opposite charges attract

  • negative and positive

• Like charges repel

  • negative and negative

  • positive and positive

electric circuits - THIS IS COMING UP

• electric circuit - path that transmits electricity

• consist of three essential items:

  • a power supply to provide the electrical energy (e.g. batteries, power packs)

  • a load or loads in which electrical energy is converted into other useful forms of energy (e.g. light, heat, sound) such as lights, heaters or a motor

  • a conducting path that allows electric charge to flow around the circuit

    • in the squishy circuit practical the play doh would’ve been the conducting path

    • must be made of conducting materials (e.g. metals)

circuit diagrams

• maps of electric circuits need to be drawn so that people all over the world can read them

• these maps are called

voltmeter

switch open

switch closed

resistor

light globe

2 wires joining

• a resistor is any device or material that makes it difficult or harder to electric charge.electrons to flow through

  • as a result of being made up of less conductive materials

• any material that is conductive that is not a wire can be represented by the load symbol (the rectangle)

• amy material that is insulating can be represented by the resistor symbol (the zig-zag one)

Current

• current: how many coulombs (number of electrons that represent one ampere) of electrons flows through a conductor per second

• 1 amp =

• 1 coulomb =

using a water hose analogy

• the flow rate

• the water pressure: how much force the water is pushing with (you can feel this if you put a finger over the end of the hose) 

  • voltage: amount of electrical energy (comes from with in a power supply) that is used to push electrons through a conductor

  • unit: voltage or v and is measured by a voltmeter

• the power: how kuch work

Energy

• represented in waves

• Energy manipulates matter

• Endothermic energy: absorbs energy

• exothermic energy: generate energy

• can change matter physically or chemically

• if it hits a valence electron it may cause the electron to hit another electron and so on to show the “flow“ of electrons

Electric current

• electric current is the amount if electric charge flowing through a wire per second

• measured in amperes (A) (or Amps for short)

• the electric charge comes from the electrons

Parallel circuits

• Branching circuits

• more that one conducting pathway for current to flow

• voltage is the same across loads

• current is split voltage is the same

Series circuits

• voltage is split current is the same

• only 1 conducting pathway

• loads connected side by side

• voltage is split across loads

Resistance

• resistance is the measure of how an object resists the flow of electrons

• resist the flow of electrons → controls

OHMs law

• ohms law is a formula used to calcualte the relationship between volatage, current and resistance in an electrical circuit

• voltage = resistance and current

• V = R x I

• Where V is in (volts/V), I is in (amps/a) and resistance is in (Ohms/Ω)