3.4 Flashcards
(29 cards)
What are the different types of methods to generate electricity?
Light
Heat
Friction
Pressure
Chemical action
Magnetism and motion
What happens if light falls upon certain semiconductors?
causes charge separation and therefore generates electricity
How are semiconductors pictured?
as a framework of fixed atoms joined by covalent bonds
A semiconductor’s conductivity depends on what?
on the rate at which the bonds are broken
Breaking of bonds releases what?
An electron and a hole
How does light increase the conductivity of semi conductors?
The energy from the light caused vibrations of atoms and therefore increased conductivity of semiconductors
What process is used to augment the conductivity of semiconductors by producing more electrons or holes?
Doping
How does doping work?
Add impurities to a semiconductor
How is a solar cell made?
A thin slice of n type silicon over a thicker slice of P type silicon
Describe of a thermal couple?
Two different metals are joined together to form a junction. A small EMF is produced across the junction due to the difference in each materials conductive properties
If temperature increases in a thermal couple what happens to EMF?
It also increases
What is a use of a thermal couple?
It is used in applications that require accuarate measurements in temperature differences
Where might thermocouples be used on an aircraft?
Sensors to measure EGT of turbine engines
Thermal couples are efficient for high-power applications. True or false?
False, they are not efficient enough for high-power applications.
Rubbing an insulator causes electrical charges…..
to separate and is a source of EMF
Personnel working with static sensitive electronic components must do what?
wear a protective bonding braid around the wrist, which is connected to earth in order to prevent the build-up of such static charge.
What two instances cause static electricity?
Static electricity can be generated whenever two materials contact or separate and at least one is a poor conductor of electricity. Static electricity also occurs when insulating liquids and gases flow.
Where does the electrical field tend to be stronger?
In the points and corners
What are static wicks used for?
dispel static charges
What is the Piezoelectric effect?
Using pressure to deform a piezo crystal generates a voltage
Is the piezoelectric effect reversible?
Yes
What applications can piezoelectric be used for?
very small and precise mechanical movements may be controlled by applying a voltage across the piezo crystal.
How does chemical action work?
two different metals, one electron deficient the other an excess of electrons are both submerged in a solution which cause current flow.
What is another word for voltage generators that use chemical action?
Galvanic cells
