A2 Advancing Physics - OCR B (Capacitance)

ADVANCING PHYSICS
CAPACITANCE
How much charge a capacitor can keep separated at a given Potential Difference.
The amount of charge stored per volt
Q
C=V

C = Capacitance, Q = Charge, V = Potential Difference

Capacitance is measured in Farads or µF
The simplest form of capacitor consists of two…

E= 12 QV
E = Energy on a capacitor, Q = Charge, V = potential difference




2
E=1
2 CV

E = Energy on a capacitor, C = Capacitance, V = potential difference

When the capacitor is connected around a resistor, the current flows in the opposite directionfrom the
charging…

-t
Q = Q0 eRC

Q = Charge left on plates, Q0= charge of capacitor when fully charged, t = Time, RC = time constant

The graphs for potential differenceor currentagainst timefor charging and discharging are also




exponential.
t
dV = Gradient of V 0e-RC
dt



dV 1 t
dt…