5.4 Capacitors Flashcards
What is a capacitor?
an electric component that stores energy in the electric field between a pair of metal plates separated by an insulator
What is capacitance?
the charge stored per volt
What unit is capacitance measured in?
Farads
Define potential difference
the work done per unit charge
When a capacitor is charging, electrons flow onto one plate and are ——– the other plate
repelled from
The capacitor stops charging when –
the emf of the battery charging it=pd across the capacitor
As the pd across the charging capacitor rises, what happens to the charging current
it decreases
What does the rate at which the pd rises across the capacitor depend on? (2 things)
- capacitance of capacitor
- resistance of circuit
When a capacitor is being charged, why does the charging current decrease with time?
It becomes more difficult to push electrons onto the plate because of the repulsion from the electrons already there
If the resistance of a circuit charging a capacitor is lowered, does the capacitor charge more or less quickly?
more quickly
As a capacitor discharges, what happens to the current?
It decreases exponentially with time
Define the Time Constant
product of capacitance and resistance
What are the 2 uses of a capacitor (in this spec)
- flash guns
- defibrillators
