Electricity Flashcards
What is AC current?
A current which changes direction and instantaneous value with time
What is electromotive force?
The electrical potential energy supplied to each coulomb of charge by the source
What is internal resistance?
The resistance within a power supply
What is an open circuit?
Where there is no current drawn from the power supply and no voltage is lost
What is a short circuit?
When there is no resistance within the circuit, it’s as if the terminals of the cell are connected with a wire
What is capacitance?
The ability of a component to store charge
What are energy levels?
Where electrons are contained within the atom
What is the conduction band?
It is the highest of the energy bands. Electrons cannot move in the valence band but are able to move freely in the conduction band
What is a p-type semiconductor?
It is made by adding indium to silicone three electrons occupy the valence band but this leaves an electron missing. This area is called a positive hole. Electrons can occupy these holes so conduction can take place
What is a PN junction?
A PN junction is made by joining p-type and n-type semiconductors. The PN junction is a device which only allows current to flow through one way
What is a depletion layer?
Is a layer formed in a PN junction when electrons move to occupy holes
What is forward bias in a PN junction?
Negative terminal connected to n-type positive terminal connected to p-type
This reduces the electric field in the PN junction
How does an LED emit light?
Electrons move towards the conduction band of the p-type. Electrons drop to the valence band. Photon is emitted
What is reverse bias in a PN junction?
When an n-type is connected to a positive terminal and the p-type is connected to the negative terminal, this increases the electric field in the PN junction.
How does a PN junction act as a solar cell?
Electrons absorb energy from photons electrons move from valence band to conduction band electrons move towards n-type semiconductor producing a potential difference.
