Lightning
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Lightning

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A set of slides created to teach Lightning to learners at Bishops Diocesan College in Cape Town.

A set of slides created to teach Lightning to learners at Bishops Diocesan College in Cape Town.

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  • 1. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Lightning K Warne
  • 2. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Lightning - Facts • Lightning is an atmospheric discharge of electricity, which usually occurs during thunderstorms. • A leader of a bolt of lightning can travel at speeds of 60,000 m/s, and can reach temperatures approaching 30,000 °C , hot enough to fuse soil or sand into glass channels. • An average bolt of lightning carries a negative electric current of 40 thousand amperes (kA) and transfers a charge of five coulombs and 500 MJ of energy. • The voltage depends on the length of the bolt, with the dielectric breakdown of air being three million volts per meter; this works out to approximately one gigavolt (one billion volts) for a 300 m (1000 ft) lightning bolt. • With an electric current of 100 kA, this gives a power of 100 terawatts. • Lightning heats nearby air to about 10,000 °C nearly instantly, which is almost twice the temperature of the Sun’s surface. The heating creates a shock wave that is heard as thunder. • Most lightning bolts are about 1.6 kilometers (1 mi) long. The longest recorded length was 190 kilometers.
  • 3. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Thunderstorm
  • 4. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Supercell
  • 5. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Charge Separation One explanation: • Clouds can contain millions upon millions of particles of water vapor, water droplets and ice suspended in the air. • Convection currents within the clouds cause collisions & friction to occur between these particles. • Electrons are knocked off of the rising vapor & moisture and transferred to falling ice particles, thus creating a charge separation. In an electrical storm, the storm clouds become charged. The upper portion of the cloud is positive and the lower portion is negative. How the cloud acquires this charge is still not agreed upon within the scientific community. + + + + + + + + + + + + + + - - - - - - - - - - - - - - -
  • 6. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Potential difference • The charge separation in a cloud, creates a potential difference and electric field between the earth surface and the cloud. • This is very similar to oppositely having two oppositely charged parallel plates close together. • The strong electric field ionises the air, creating a conductive path for the negative cloud bottom to contact the positive earth surface. • If the potential difference is large enough the charge is able to flow between the cloud and earth surface.
  • 7. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Lightning Stages
  • 8. SAMPLE ONLY SAMPLE ONLY SAMPLE ONLYForFor FULLFULL presentation clickpresentation click HERE >> ScienceCafeHERE >> ScienceCafe Hi - This is a SAMPLE presentation only. My FULL presentations, which contain loads more slides and other resources, are freely available on my resource sharing website: www.sciencecafe.org.za (paste into your browser if link above does not work) Have a look and enjoy! Keith Warne