Electricity Flashcards
How do u find the peak voltage using an oscilloscope
Y gain setting x number of divisions
How do u calculate the period of waves using an oscilloscope
Time base setting x number of divisions
Current and voltage in a series circuit
Current is equal all over
Voltage adds up
Current and voltage in a parallel circuit
Current adds up
Voltage is equal all over
If u increase the resistance…
Current decreases
How can the voltage across a Wheatstone bridge be determined…
By calculating the voltage across each of the bottom resistors in the potential dividers and then calculating the difference between these two voltages.
What voltage is measured in an open circuit
EMF
Terminal potential difference
The energy per unit change available at the terminals of the electrical source
What is a capacitor?
An electrical component that stores electrical charge
Capactiance
Charged stored per volt
Farad
One Colomb of charge per volt of potential difference
Increasing the capacitance
Increases the time taken for the capacitor to charge/discharge
Increasing the resistance of a capacitor
Increases the time for a capacitor to charge/discharge
Conductors have…
Many free electrons which can easily move through the materials
Insulators have…
Very few free electrons
Semiconductors are…
Insulators are pure won’t conduct but they will conduct when an impurity is added or when exposed to heat/light
Band theory for a conductor
The highest occupied band is not completely full so electrons can move and therefore conduct. (Conduction band) the valence band is full so electrons can’t move. At room temp the valence band overlaps the conduction band this assists conductions
Band theory for an insulator
Valence band is full so no movement therefore no conduction. The gap between the valence and conduction band is large so there is not enough energy available to move the electrons from the valence to the conduction band. Therefore there is no conduction in insulators.
Band theory for a semiconductor
The gap between the valence and conduction band is small, so at room temp there is sufficient energy to move some electrons from the valence to the conduction bands, therefore some conduction takes place. The electrons also leave holes I. The valence band which allows for further conduction to take place.
(Conductivity) Increasing the temperature….
Increases conductivity in a semiconductor
Doping is when…
The electrical properties of semiconductors are altered
N-type semiconductor…
Provides extra electrons. The extra electrons occupy energy levels close to the conduction band and therefore easily excited into the conduction band. Majority of carriers are negative
P-type semiconductor
Has less electrons. Gaps at energy levels just above the valence band, therefore they are easily excited into these levels leaving behind holes in the valence band. Majority of carriers are positive.
What is a p-n junction?
When two different types of semiconductors are placed in contact with each other
Photovoltaic effect
When photons with sufficient energy go into the p-n junction giving the electrons enough energy to move from the valence band to the conduction band, this allows for a current to be drawn
What is the Vlost equation
Vlost = Ir
That is the equation that connects Vlost Vtpd and E
E= Vtpd + Vlost
Using band theory explain how an LED emits light
-Electron moves towards the conduction band of the p-type
-Electrons move from the conduction band to the valence band
-A photon is emitted
