Capacitors Flashcards
What is the equation for capacitance?
C = Q/V
What are capacitors?
Capacitors hold charge
What are used for capacitors?
Flash photography, defibrillators, backup power supplies
What’s are the 2 equations for energy stored by a capacitor?
E = 0.5QV
AND
E = 0.5CV^2
How are capacitors charged?
The capacitor is connected to a battery. An equal but opposite charge builds up on each plate of the capacitor. When the pd across the capacitor = the pd across the battery, the capacitor is fully charged.
What is the current across a capacitor like?
When the capacitor is charging the current is high, but when the capacitor is fully charged the current is 0
How do you discharge a capacitor?
Remove the battery and reconnect the circuit
What 2 factors affect how long it takes to charge or discharge a capacitor?
The capacitance of the capacitor, and the resistance of the circuit
What is the definition of capacitance?
The ammount of charge stored per volt
What is discharge rate proportional to?
Charge remaining
What is the equation for rate of discharge?
dQ/dt = -Q/RC
When a capacitor is discharging, how does the amount of charge change?
It falls exponentially with time. This means it always takes the same length of time for the charge to halve
What is the equation for charge on a discharging capacitor?
Q = Q0 * e^-t/RC
What is the equation for voltage on a charging capacitor?
V = V0 - V0*e-t/RC
What is the equation for voltage on a discharging capacitor?
V = V0*e^-t/RC
