Zusammenfassung der Ressource
Capactiors
Anlagen:
- Capacitor Basics
- Capacitors are devices that
store electrical charge.
They are made by having 2
metal plates separated by
an air gap.
- The amount of charge a capacitor can
store per volt is the capacitance (C)
measured in Farads (F). It can be
calculated using the potential
difference across the capacitor when
fully charged, and the charge stored
(Q)
- Charging and Discharging
Capacitors
- When a power supply is connected
to a capacitor, positive and
negative charge build up on
opposite plates. This creates a
potential difference. This creates a
uniform electric field between the
plates.
Anmerkungen:
- The charging and discharge of a
capacitor happens exponentially
(starts off quick, then slows
down.)
- If a capacitor is disconnected from a cell and
then used connected to a resistor, it'll
discharge. This is because the electrons will
move over to the positive side of the
capacitor and by discharging through a
resistor.
- We can calculate the new voltage (V)
after a given amount of time
discharging (t) given that we know the
initial voltage (Vo) and the time
constant of the capacitor (RC)
- The equations for the charge and discharge of a
capacitor all follow the same pattern to show
the changes in charge, current and voltage
- The time constant is the time a
capacitor will take to discharge down to
37%.
- If we know the capacitance of the capacitor (C), and
the resistance of the resistor (R) that it is discharging
through, we are able to calculate the time constant
of the capacitor
- T=RC
- Energy stored in a
capacitor
- A charged capacitor is a
store of electrical potential
energy. When the capacitor
discharges, electric potential
energy is transferred into
other forms.
- When calculating electric potential
energy, our value is halved. This is
because work is done when charging
a capacitor, this leads to some
energy being dissipated.
- This leads to the energy
stored being the area under a
Voltage (V) against Charge (Q)
graph.