Electricity Glossary Terms - Chapter 11

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Electricity Glossary Terms - Chapter 11
2014-10-23 23:48:11

Grade 9 Science Electricity Terms - Chapter 2 of 3
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  1. Electric Circuit
    • def: a closed path along which electrons that are powered by an energy source can flow
    • e.g: a flashlight when switched on

  2. Voltaic Cell
    def: a source of energy that generates an electric current by chemical reactions involving two different metals or metal compounds separated by a solution that is a conductor

  3. Battery
    • def: a connection of two or more cells
    • e.g: a battery is made when two or more cells are placed in a flashlight

  4. Electrode
    • def: one of two metal terminals in a cell or battery
    • must be made of different materials
    • breakdown of electrodes is a factor that can limit the life of a battery

  5. Electrolyte
    • def: a solution or paste that conducts charge
    • electrodes are immersed in electrolytes

  6. Dry Cell
    • def: a cell that contains an electrolyte that is a paste
    • most cells used are classified as dry cells

  7. Wet Cell
    • def: a cell that contains a liquid electrolyte
    • most wet cells use a solution of sulfuric acid as an electrolyte

  8. Primary Cell
    • def: a cell that can only be used once before it is discarded
    • used in calculators, hearing aids, computers, and toothbrushes
    • e.g: zinc-carbon cell (D cell), alkaline cell, silver-oxide cell, and zinc-air cell

  9. Secondary Cell
    • def: a cell that can be recharged
    • electric current is passed in the opposite direction through the cell, which reverses the chemical reactions in the cell
    • e.g: the lead-acid battery used in trucks, automobiles, and motorcycles

  10. Fuel Cell
    • def: a cell that generates electricity through the chemical reactions of fuel that is stored outside the cell
    • only by-products of the reaction are heat and water
    • can provide energy for automobiles, buses, and small devices such as cell phones
    • e.g: hydrogen fuel cell combines hydrogen that is stored in a tank or cartridge with oxygen from the air

  11. Solar Cell
    • def: a cell that converts sunlight into electrical energy
    • e.g: when sunlight strikes a semi-conductor, electrons are knocked loose from the atoms. A few small solar cells can provide enough energy for a calculator or ornamental garden light and large solar panels can operate a satellite

  12. Terminal
    • def: location on a cell that must be connected to other components to form a circuit
    • to create a battery that works properly, the oppositely charged terminals of the cells must be in contact with each other

  13. Switch
    • def: a control device that can complete or break the circuit to which it is connected
    • not needed for a circuit to operate, but is convenient

  14. Open Circuit
    • def: a circuit that contains a gap or break
    • e.g: if a bulb is loose and does not make contact with the base of its socket, the circuit is open and the bulb will not glow

  15. Electric Current
    • def: the rate (time) of movement of electric charge
    • in an electric circuit, the current is due to the flow of electrons
    • e.g: the flow of water is an analogy for the flow of electrons through a conductor. It is unlikely for you to think of individual molecules passing by, but instead you might think about a very large amount of water passing by. (same for electric current)

  16. Coulomb (C)
    • def: one coulomb is the quantity of charge that is equal to the charge of 6.25 x 1018 electrons
    • the electric charge passing by a point in a circuit is measured in terms of a very large number of electrons
  17. Ampere (A)
    • def: the unit of electric current, equivalent to one coulomb per second (1C/s)
    • measured using an ammeter

  18. Electrical Resistance
    • def: the property of a substance that hinders electric current and converts electrical energy to other forms of energy
    • electron in a circuit do not get very far before colliding with other ions or electrons. the collision interfere with the flow of electrons.
    • metals have a lower resistance, which is why they are used to make circuit connections
  19. Resistor
    def: a device used in an electric circuit to decrease the current through a component by a specific amount

  20. Load
    • def: a resistor or any other device that transforms electrical energy into heat, motion, sound, or light
    • e.g: an oven transforms electrical energy into heat (mostly) and light to be able to cook food

  21. Potential Difference (voltage)
    • def: the difference between the electric potential energy per unit of charge at two points in a circuit (Electrical Potential Energy Difference)
    • there is no such thing as voltage at a single point in a circuit
    • all forms of energy are measured n joules (J)
    • Potential Difference=difference in potential energy (J)/charge (C)
    • measured using a voltmeter

  22. Volt
    • def: the unit for potential difference, equivalent to one joule (J) per coulomb (C) (1J/C)
    • e.g: a cell marked 1.5V will do 1.5J of work moving a coulomb of electrons through the circuit
    • an electric charge does not lose energy when it moves along a perfect conductor with no resistance
  23. Circuit Diagram
    def: a diagram that uses standard symbols to represent the components in an electric circuit and their connections

  24. Series Circuit
    • def: a circuit in which there is only one path along which electrons can flow
    • e.g: a flashlight is a series circuit because it has a power source, a light bulb, and a switch all on the same path

  25. Parallel Circuit
    • def: a circuit in which there is more than one path along which electrons can flow
    • e.g: Christmas light are a parallel circuit because there is more than one path that the electrons can take

  26. Ohm’s Law
    • def: the ratio of potential difference to current is a constant called resistance
    • V=potential difference (volts, V) V=IR
    • I=current (amps, A) I=V/R
    • R=resistance (ohms, Ω) R=V/I
    • the larger the resistance, the smaller the current
  27. Ohm (Ω)
    • def: the unit for resistance, equivalent to one volt per ampere (1V/A)
    • symbol for the ohm is the Greek letter omega Ω
  28. Superconductor
    • def: a material through which electric charge can flow with no resistance
    • does not transform electrical energy into heat
    • very powerful magnets are made using superconducting wires. These magnets are used to accelerate particles

  29. Non-Ohmic
    • def: not following Ohm’s Law
    • if the ratio of potential difference between the ends of a load to the current through the load changes, then the load does not have constant resistance and does not obey ohm's law
    • e.g: the filament in an incandescent light bulb is non-ohmic because its resistance increases with temperature. The greater the resistance of the filament, the more electrical energy is turned into light and the brighter the bulb glows.
  30. Loads in Series
    • Current: same at all points because there is only 1 path for the electrons to travel IT=I1=I2=I3
    • Potential Difference:splits up because energy has to be shared by all of the loads, but the sum is equal to the source supply. If loads are identical, the potential difference will split equally, if not the more resistance the more energy required VT=V1+V2+V3
    • Resistance: the more loads in a series circuit, the greater the resistance. Total resistance is equal to the sum of the resistance through each load RT=R1+R2+R3
    • As more bulbs are added in series, each bulb will glow with less intensity because resistance will increase, causing current to decrease. If bulbs are identical, they all glow with the same intensity and if one goes out, they all go out.

  31. Loads in Parallel
    • Current: will split up because there is more than 1 path for the electrons to travel. If all loads are identical, current will split equally, if not more resistance on that path the less current will travel down that path IT=I1+I2+I3
    • Potential Difference:same down each path because the electrons are splitting up but the energy that they are carrying is the same VT=V1=V2=V3
    • Resistance: the more paths in parallel, the less down each path RT<R1; RT<R2; RT<R3
    • As identical bulbs are added, the brightness of the bulbs stays the same because each path receives the same amount of energy and if one bulb goes out, the rest stay on.