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Electricity

Electricity. Review – The Atom. All matter is made of tiny particles called atoms . Atoms are made of 3 different types of particles: Protons Neutrons Electrons. Review – Atomic Structure. Neutron. Proton. -. +. -. Electron. Nucleus. Review – Atomic Charge.

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Electricity

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  1. Electricity

  2. Review – The Atom • All matter is made of tiny particles called atoms. • Atoms are made of 3 different types of particles: • Protons • Neutrons • Electrons

  3. Review – Atomic Structure Neutron Proton - + - Electron Nucleus

  4. Review – Atomic Charge • A neutral atom has the same number of protons as electrons. Eg. A neutral oxygen atom has 8 protons and 8 electrons.

  5. Review – Atomic Charge • Electrons can be removed from an atom, resulting in a positively charged atom. - + Positive Neutral + -

  6. Review – Atomic Charge • Electrons can also be added to an atom, resulting in a negatively charged atom. - - Negative Neutral + -

  7. Review – Atomic Charge • An atom with an uneven number of protons and electrons is called an ion. • Electrons can be separate from atoms and can move freely within and between certain substances. • This is why metals conduct electricity.

  8. What is Electricity? • Electricity is a convenient type of energy that travels very fast and can be transformed into a variety of other types of energy.

  9. Types of Electricity • There are two types of electricity.

  10. Static Electricity • Static E occurs within insulators. • When the insulator is rubbed electrons are either added or removed, and the object is charged. + -

  11. Static Electricity • When a plastic rod is rubbed with a wool cloth, the rod will lose electrons to the cloth and become positively charged. • The wool becomes negatively charged. + + - + - + - - - + - +

  12. Static Electricity • Static electricity is caused by a surplus or deficiency of electrons in an object. • The object holds stored electrical energy. - - - - - -

  13. Static Electricity • If two objects have opposite charges they will attract each other. • If they have the same charges they will repel. - + - -

  14. - + - - + + - + + - - + + - - + + - - + - + + - -

  15. Current Electricity • Electrical currents happen when free electrons travel from an area which is negatively charged to an area which is positively charged. • Electricity needs a continuous pathway (circuit) in order to flow.

  16. Current Electricity • A substance like copper has free electrons and is an electrical conductor. • Plastic is said to be an electrical insulator because it does not have free electrons.

  17. Circuit Diagrams

  18. Current Electricity • A circuit consists of at least 3 main parts: • An energy source (e.g.. battery). • An energy user (e.g.. light bulb). • A complete conducting pathway (wires)

  19. Circuit Diagrams • Draw a simple circuit showing one light bulb controlled by a switch and powered by 2 cells.

  20. Measuring Current • When electrons flow around a circuit they create current. • We can measure the amount of electrons flowing in a circuit with an ammeter. • The symbol for current is I, because it describes the intensity of the current.

  21. A Measuring Current • The ammeter measures in units called amperes (or amps) and is represented by the symbol A. • In circuit diagrams we represent an ammeter by the symbol:

  22. Current A - - - -

  23. Measuring Current • An ammeter must be connected in series at the point where you wish to measure the current. A

  24. Types of Current • There are 2 types of current: • Direct Current (DC) – Electrons flow in only one direction. (E.g. Battery powered devices) • Alternating Current (AC) – Direction changes 50 times a second. (E.g. Electricity from mains)

  25. Measuring Energy • Current in a circuit carries electrical energy. • Electrons gain energy from the energy source and lose energy from the energy users, where it is converted into other forms.

  26. Measuring Energy • Voltage gain – the increase in electrical energy. • Voltage loss – the decrease in electrical energy. • We represent the gain or loss in voltage by the symbol V.

  27. V Measuring Energy • The unit for voltage is the volt and can be measured with a voltmeter. • In circuit diagrams we represent an voltmeter by the symbol:

  28. Measuring Energy • A voltmeter can only measure the change in voltage so it must be connected in parallel around a lamp or battery. V

  29. Measuring Energy • The amount of voltage lost at an energy user is equal to the amount of voltage gained from the batteries. • In a series circuit the voltage loss is shared between components. • In parallel the voltage loss is the same in both components.

  30. Electrical Conductors • Conductors are materials that allow the flow of electric charge. Metals are good conductors. • Insulators are materials that do not allow the flow of electric charge. Plastic is an example of a good insulator.

  31. Electrical Conductors • It is the delocalized electrons involved in metallic bonding that allow metals to conduct electricity. • The delocalized electrons are free to flow through the metal and so carry a current. • Insulating materials do not contain free electrons and so current is unable to flow.

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