3.4 Generation of Electricity Flashcards
How is static electricity generated?
Via friction between two insulating materials rubbing together.
How do you find out which materials become positive and which negative when rubbed together?
Triboelectric chart, Higher on the chart = positively charged (loses electrons), lower on chart = Negatively charged (gains electrons)
Aircraft utilise static dischargers and position them where?
To minimise interference with radio systems where friction can pick off the positive or negative charge.
How do crystals (quartz) generate voltage?
When ever stresses are applied to their surfaces: pressure, squeezed.
What is the piezo electric effect?
Using crystals to convert mechanical energy into electrical energy.
What is used to generate electricity from pressure.
Piezoelectric materials: crystalline materials, quartz.
How is the voltage produced in a piezoelectric material?
When pressure is applied the voltage is produced by the changing charge created by the moving electrons
What is used to generate electricity from heat.
Thermocouples
How does a thermocouple operate?
By using 2 dissimiliar materials/conductors, iron and copper. that move the electrons from cold junction to the hot(iron) and then hot junction to cold (copper)
What directly effects the thermoelectric voltage output of a thermocouple?
The difference in temperature between the hot and cold junctions.
What are thermocouples mainly used for?
Measure temperature and used in heat sensing devices.
What is used to generate electricity from light?
photovoltaic cell, photosensitive metal
Explain photoelectric voltage
The photosensitive metal loses electrons from the lights intensity making it positively charged creating an electric force.
Photosensitive materials most commonly used are?
various compounds of silver oxide or copper oxide
What controls the amount of electrons emitted from the photo emissive material?
The intensity of the light source.