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ELECTRICITY

ELECTRICITY. Chapter 13.2 – 13.3 VOLTAGE / AMPERAGE / WIRE / BATTERY / SERIES / PARALLEL / MULTIMETER. VOLTAGE – page 438-439. An electric charge has potential electrical energy . The unit for measuring potential electrical energy is the volt .

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ELECTRICITY

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  1. ELECTRICITY Chapter 13.2 – 13.3 VOLTAGE / AMPERAGE / WIRE / BATTERY / SERIES / PARALLEL / MULTIMETER

  2. VOLTAGE – page 438-439 • An electric charge has potential electrical energy. • The unit for measuring potential electrical energy is the volt. • A common source of potential energy is a battery. • A battery converts chemical energy into electrical energy. • A voltage that sets charges in motion may commonly range from 1.5 – 24 volts in batteries. • Voltages are much higher in electrical outlets.

  3. AMPERAGE – page 439 • Electrical current is the movement of electricity from one location to another usually through wires. • It is due to the movement of a charge from a place of high potential to one of low potential. • An ampere (amp) is the measure of the amount of current flowing through a circuit. It is the rate that electric charges move through a conductor.

  4. OHM – page 441-445 • An OHM is a measure of the resistance (friction) in a circuit. • Some things that resist the flow of electricity are: • Thin wire (dimmer light bulbs – thin wire does not let as many electrons flow through the wire so the light is not as bright) • Some types of metals (tungsten in light bulbs) • High temperature (as a circuit heats up it creates more resistance!) • Resistance produces HEAT and if there is enough heat it produces LIGHT.

  5. OHM /AMPERE / VOLT – The relationship between these can be calculated using : • ohms = volts amperes • Materials with low resistance are called conductors. • Materials with high resistance are called resistors or insulators (depending on how used) • Superconductors are materials that have zero resistance below a certain temperature. • Semiconductors are materials with electrical properties between conductors and insulators.

  6. WIRE CHARACTERISTICS • SIZE • Thickness determines how easily electricity can flow in a circuit. • MATERIAL • Some metals are better conductors than others. • Most home and auto wiring is COPPER • Some electronics may be gold or silver • INSULATED / NOT INSULATED • Bare wire…no insulation • Plastic or rubber covered wire • Varnish covered used in motors and electromagnets.

  7. BATTERY CHARACTERISTICS • Size • Depends on application and power needs. • Voltage • Does not depend on size…may be large or small • Amperage • Depends on size…larger = more amps • Materials – determine strength, longevity, charge ability. • Carbon zinc • Nickel-cadmium • Silver oxide • Lithium

  8. 13.3 CIRCUITS - SERIES CIRCUIT • A SERIES CIRCUIT has only one path for the current to travel. All the current must go through each part of the circuit. • A major problem with this is that if one part of the circuit is broken (burned out bulb etc.) the whole circuit goes dead. • Also the resistance keeps increasing as the circuit gets larger. This means that as bulbs are added to a series circuit they do not burn as brightly as when there are fewer bulbs.

  9. PARALLEL CIRCUIT • A PARALLEL CIRCUIT has separate paths for the current to flow. • If the current in one path is broken, the current can still flow in the other paths. If one bulb burns out, the rest remain on. • Resistance is not affected by how many bulbs are in the circuit. Each bulb burns as brightly as when there were fewer bulbs.

  10. FUSES and CIRCUIT BREAKERS • Protect circuits from overheating because of … • Overloaded circuit • Overheats because resistance is lowered as objects are added to the circuit • Short circuit • Overheats because there is no resistance

  11. This wires in fuses melt when overheated Circuit breakers open the circuit when overheated How FUSES and CIRCUIT BREAKERS work • Fuses and breakers are connected in series

  12. MULTIMETER • DC VOLTS - up to 1000 volts may be measured • AC VOLTS – up to 750 volts can be measured. • DC 200 and 2000 u is a very small value for amps. • DC 20 and 200 mA (miliamps) is a small value for amperes. • DC 10A (amperes) is the largest value for amps this meter can read. • The red test lead plugs into the V/mA jack for testing voltage and for small (milli-amp) currents • The red test lead also is moved to the 10A for larger (10 ampere) currents. • The black test lead always plugs into the blackCOM (common) jack.

  13. Measuring amperage – break the circuit and place the meter in series with the circuit. Always start testing an unknown on the 10A setting unless told to do otherwise! Measuring voltage – set the selector to DC for battery circuits. A V or mV will appear on screen. A “–” on the left side means your polarity is negative. Switch lead positions for positive readings. Using the Multimeter

  14. Study for the Test: • Vocabulary • Factors that change resistance…high or low • Characteristics/examples of series and parallel circuits • Characteristics/examples of conductors and insulators • Schematic drawings…know the symbols so you can draw a diagram

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