1 / 23

Electricity

Electricity. Electrical Quantities. Electrical energy. All electrical charges possess electrical energy. The energy possessed by an electric charge depends on: Whether or not it is in motion. (kinetic) Where and how it is located. (potential). Conversion of electrical energy.

kosey
Download Presentation

Electricity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Electricity Electrical Quantities

  2. Electrical energy • All electrical charges possess electrical energy. • The energy possessed by an electric charge depends on: • Whether or not it is in motion. (kinetic) • Where and how it is located. (potential)

  3. Conversion of electrical energy • All electricity is converted to one form or the other. • In a heater, kettle, or iron it is converted to heat. • In a motor it is converted to kinetic energy, as in a fan. • Sometimes movements are converted to electricity, eg in a hydroelectric power station

  4. Electric Potential Energy • The potential energy of a charge is due to its position in an electric field. • The difference in the electric potential energy of a charge between two points in an electric field is known as the Potential Difference. • Potential Difference is called the voltage, V and is found by the equation: Where E is the difference in potential energy and Q is the charge as it moves along the electric field.

  5. Potential Difference • We see from the equation that the S.I. unit of V may be seen as the “ joule per Coulomb”, JC-1. • This unit is named the “volt” for which the symbol is V, i.e. 1 V = 1 JC-1.

  6. Electrical Power • This is the rate at which electrical energy is being consumed. • Electrical Power is defined as the rate at which energy is being produced, transmitted or converted. • Remember the S.I. unit of power is the Js-1 or Watt (W). Here the Watt is defined as ampere-volt i.e. 1 W = Js-1= 1 AV and so But power by definition is So,

  7. The Kilowatt – hour (kWh) • This is the energy involved when a power of one kilowatt is maintained for one hour. • A kWh can be converted to joules as follows: P = E/t , where P = 1 kW= 1000W t = 1hr = 3600 s Therefore E = Pt = 1000 × 3600 = 3600000J = 3.6 ×106J

  8. Circuit and components • You are to know how to use circuit symbols in drawing circuits

  9. Circuits • An electrical circuit is a continuous pathway along which electric charges are kept in motion by a source of electromotive force (e.m.f.). • There are two (2) main types of circuits: series and parallel.

  10. Circuit diagrams

  11. Series Circuit • A series circuit is one in which the current is the same in all parts of the circuit. • All components and devices are connected in one loop

  12. Series Circuit

  13. Parallel Circuit • A parallel circuit is one where there are multiple loops or branches. • The main current drawn from the source splits (divides) itself into the different branches. • In a parallel circuit, the voltage (potential difference) across each branch is the same.

  14. Parallel Circuit

  15. Is it series or parallel

  16. Sources of E.M.F. • It is a source of energy that can cause a current to flow in an electrical circuit or device. It is measured in volts. • Chemical cells, dynamos or generators, power supply units, solar cells and thermocouples are all sources of emf. • Chemical cells (comes in wet and/or dry) are the most popular and are of two types: primary or secondary.

  17. Primary Cells • A primary cell is one where chemical energy is converted to electrical energy. The chemical reaction that causes this cannot be reversed. • Therefore, these cells cannot be recharged. • Eg are the Daniell cell, the Leclanché cell, the Weston cell and the mercury cell.

  18. Secondary cells • Again chemical energy is converted to electrical energy, however, the cell CAN BE RECHARGED by reversing the current through it. • Eg are the lead-acid cell, nickel- iron (NiFe) cell, nickel-cadmium (Nicad) cell (These are the “button” cells you see in watches and calculators).

  19. The Leclanché (Zinc-Carbon) cell

  20. Parts of this cell • The carbon rod is the anode. (+ve) • The zinc case is the cathode. (-ve) • The ammonium chloride paste is the electrolyte. • The manganese oxide mix is a depolarizing agent. This removes the hydrogen that collects at the anode (carbon) which can lower the emf.

  21. How it works? When you connect the battery to a lamp and switch on, chemical reactions start happening. One of the reactions generates positive ions (shown here as big yellow blobs) and electrons (smaller brown blobs) at the negative electrode. The positive ions flow through the electrolyte to the positive electrode (from the green line to the red one). Meanwhile, the electrons (smaller brown blobs) flow around the outside circuit (blue line) to the positive electrode and make the lamp light up on the way.

More Related