Electricity Flashcards
What is current?
the rate of flow of charge
What is a semiconductor?
the resistance of a semiconductor decreases when its temperature is raised
What is potential difference?
work done per unit charge
What is the emf of a source?
the electrical energy produced per unit charge passing through the source
What is ohm’s law?
the pd across a metallic conductor is proportional to the current through it, provided the physical conditions do not change
What is a superconductor?
a material that has zero resistivity at and below a critical temperature that depends on the material. No heat loss occurs as there is no resistance
What is a positive temperature coefficient?
increase of temperature causes an increase in resistance
What is a negative temperature coefficient?
resistance decreases as temperature increases
pd of components in series and parallel
pd across components in parallel is the same
pd across components in series can be added to find the total pd.
Resistors in series
resistors in series can be added to find the total resistance
What is the internal resistance of a source?
the loss of potential difference per unit current in the source when current passes through it.
When is maximum power delivered to the load?
when the load resistance is equal to the internal resistance of the source
What can a potential divider be used for?
to supply a fixed pd
to supply a variable pd
to supply a pd that varies with certain conditions such as temperature
Potential dividers
the supply pd is split proportionally between the resistors depending on their resistance.
What is the potential divider equation?
V1 / V2 = R1 / R2
