3.4 Generation of Electricity Flashcards
What happens when light falls upon certain semiconductors?
It may cause charge separation and therefore generate electricity
Examples of semiconductors include silicon and germanium.
How does the model for conduction of electricity in semiconductors differ from that in metals?
Semiconductors are pictured as a framework of fixed atoms joined by covalent bonds, unlike metals which have free electrons
In semiconductors, holes behave as positive charges.
What is the effect of thermal energy on semiconductor conductivity?
Increases the vibration of atoms, thereby increasing conductivity
The breaking of bonds releases an electron and a hole.
What is a photovoltaic cell made of?
A thin slice of n-type silicon over a thicker slice of p-type silicon
This structure creates a p-n junction.
What is the role of the p-n junction in a photovoltaic cell?
Electrons and holes flow across it, generating Electromotive Force (EMF)
Metal strips on the surfaces act as terminals for electrical power.
What phenomenon does a thermocouple utilize to generate EMF?
The thermoelectric effect
It involves two different metals twisted or welded to form a junction.
What is the maximum voltage that can be generated by friction?
Up to thousands of volts
This can cause shocks or damage to electronic components.
What occurs when two materials contact or separate, and at least one is a poor conductor?
Static electricity is generated
Everyday examples include rubbing a balloon on clothing.
What does the electric field represent between two oppositely charged bodies?
The area where an electric charge would feel the attractive or repulsive force
The strength of the field is higher where the lines are closer together.
What is the piezoelectric effect?
Using pressure to deform a piezo crystal generates a voltage
This effect is reversible; applying voltage generates mechanical strain.
What generates voltage in a galvanic cell?
The separation of charge between two different metals in an electrically conducting liquid
An example is immersing copper and zinc in water with sulphuric acid.
What is the generator effect?
An EMF is induced across a conductor moving through a magnetic field
This principle underlies the operation of dynamos and alternators.
What increases the induced voltage in electromagnetic induction?
Magnetic field strength, movement speed, and effective length of the conductor
This principle is crucial in engineering applications.
What do most electrical generators use instead of permanent magnets?
Electromagnets arranged in a static ring called the stator
The rotating coils on an axle are referred to as the rotor.
