What are the three categories of materials based on their ability to conduct electricity?
Insulators, conductors, and semiconductors.
What is a characteristic of insulators?
They do not allow electrons to flow through them.
What is a characteristic of conductors?
They allow electrons to flow through them easily.
What defines a semiconductor?
They behave as insulators when pure but can conduct under certain circumstances when impurities are added.
What are the valence and conduction bands?
Valence band is where outer electrons normally occupy; conduction band is above it and can conduct when an electric field is applied.
What happens to electrons in an insulator at room temperature?
There is not enough energy to move electrons from the valence band to the conduction band.
How does temperature affect the conductivity of semiconductors?
An increase in temperature increases conductivity as electrons gain energy to move into the conduction band.
What is doping in semiconductors?
The process of adding impurities to alter the conduction properties of a semiconductor.
What is n-type semiconductor material?
Material that has extra electrons available for conduction due to the addition of atoms like arsenic.
What is p-type semiconductor material?
Material that has holes in the valence band due to the addition of atoms like indium.
What is a depletion layer in a p-n junction?
A layer devoid of charge carriers formed when electrons and holes migrate across the junction.
What happens when a diode is reverse biased?
The depletion layer increases, and the diode does not conduct.
What happens when a diode is forward biased?
The depletion layer disappears, allowing current to flow through the diode.
What is a light-emitting diode (LED)?
A diode that emits light when forward biased as electrons fall from the conduction band to the valence band.
How does a photovoltaic cell work?
When light hits the cell, it energizes electrons to jump to the conduction band, creating an electric current.
What determines the wavelength of light emitted by an LED?
The energy loss of the electron as it falls from the conduction band to the valence band.
What is the role of solar cells?
To convert solar energy into electrical energy.
What is the effect of light intensity on solar cells?
The amount of energy produced depends on the amount of light falling on them.
What is the significance of the energy gap in semiconductors?
It determines the ability of electrons to move from the valence band to the conduction band.
What is a characteristic of n-type material regarding charge neutrality?
It is electrically neutral as all electrons are balanced by protons.
What creates a positive hole in p-type material?
The absence of an electron in the valence band due to the replacement of atoms with those having fewer valence electrons.
How do positive holes move through p-type material?
They capture neighboring electrons, effectively moving through the material.
What happens at the junction of n-type and p-type materials?
A depletion layer forms due to the migration of electrons and holes.
What is the primary function of a diode?
To allow current to flow in one direction while blocking it in the opposite direction.
