Electricity Flashcards
Explain why a reverse biased p-n junction will not conduct.
. Energy is supplied to the p-type material by the battery.
. This increases the internal electric field strength.
. The electrons in the conduction band of the n-type do not have enough energy to overcome the larger potential difference of the electric field.
. Electrons cannot pass into the conduction band of the p-type so the p-n junction will not conduct.
Explain how an n-type semiconductor can be created.
The semiconductor has impurities added that have five electrons in its outer shell. Four of these are used to fill the valence band. The fifth electron is in the conduction band. This is free to move and so conduction increases.
What is the definition of 1 amp?
1 Coulomb of charge passing a point in 1 second.
How is a p-n junction connected in reverse bias?
Connect n-type to positive of supply Connect p-type to negative of supply
What is the terminal potential difference, Vtpd?
It is the potential difference which is available to the circuit when the circuit is complete and current flows.
What is potential difference?
The number of Joules of energy transferred per Coulomb of charge.
Describe the shape of a graph of current in a capacitance circuit against time for charging a capacitor.
Starts from a maximum value and decreases to zero.
In which mode is this operating?
Explain why an LED may not produce light EVEN when it is forward biased and connected to a supply voltage.
The electrons in the n-type conduction band are not provided with enough energy to move into the conduction band of the p-type.
What is capacitance?
The charge stored per volt.
Describe the shape of a graph of voltage across capacitor against time for charging a capacitor.
Starts from 0V. Increases to the supply voltage.
