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Book Light

Book Light. Push Button Switch. Light Emitting Diode. 2 - AAA Batteries. Circuit Diagram. LED Diode. Diode is a one-way electrical switch that passes current in one direction. The LED emits light of a certain wavelength (i.e. color) Constructed with a semiconductor material.

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Book Light

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  1. Book Light

  2. Push Button Switch Light Emitting Diode 2 - AAA Batteries Circuit Diagram

  3. LED Diode • Diode is a one-way electrical switch that passes current in one direction. • The LED emits light of a certain wavelength (i.e. color) • Constructed with a semiconductor material

  4. A semiconductor is a material that in it pure form does not conduct electricity well. Silicon is a common semiconductor with four electrons in its outer shell. A silicon atom shares electrons with four neighboring atoms allowing the outer shell to be filled completely. http://www.thenakedscientists.com

  5. By substituting some of the Silicon with atoms that have five (instead of four) outer electrons, there are electrons left over to roam • By substituting some of the Silicon with atoms that have three outer electrons there are ‘holes’ created. Negatively doped Silicon Positively doped Silicon

  6. P-type Dopant N-type Dopant

  7. Electrons and holes are pushed toward junction when a positive voltage is applied to the P-side

  8. At the junction, Electrons and Holes recombined

  9. Energy in the form of light is given off when an electron and hole combine. A roaming electron has more energy than an electron bound to an atom (in a hole). That energy is given off as light.

  10. Electrons and holes swept away from junction when a negative voltage is applied to the P-side, so no current flows in circuit

  11. What makes the light white? • LEDs usually emit one wavelength (color) of light. • Most White LEDs use a blue LED (GaN) covered with a yellow phosphor coating. The yellow mixed with blue appears white. A phosphor material emits light when exposed to radiation. In this case the phosphor is “excited” by the blue light and in turn emits yellow light.

  12. Pre-assessment #4 • How does a LED and diode work? • Next two tests (review updated schedule) • Oral presentations • Book Report • Bring CDs and music sources (MP3s, etc.) on Monday • Other motors (4-pole, reed switch) • Makes sure and pick up graded stuff • Get handouts • Speakers, recording sounds, transmitting data

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