A Capacitor is an

It is made of

Capacitors only let

**electrical circuit component**. It temporarily stores charge.It is made of

**two metal plates**separated by an insulator. When a p.d. is put through the capacitor electrons gather on the negative plate whilst the same amount of electrons are removed from the opposite plateCapacitors only let

**charge travel in one direction**through them.**Capacitance**- The ability of a body to store charge (in Farads).**Farad**- One unit charge per one unit potential difference__Q__= C**V****Capacitors in a Circuit**

In a

**parallel circuit**, because there is the**same p.d.**and same**charge**through each capacitor, the total capacitance is the sum of the capacitorsIn a

**series circuit**, because the**p.d. is different**and there is the**same charge**through each capacitor, the total capacitance is the sum of the inverse values of the capacitors.These are the opposite equations to the

**from AS***Resistor equations***Energy of a Capacitor**

The area of a Charge to p.d. graph will give he energy of charged capacitor

**Discharging of a capacitor**

A Capacitor discharges

**exponentially.**This means the ratio remains constant between the starting and final current over an time periodThe equations for this discharge are shown below.

**Q0**is original charge

**I0**is original current

**V0**is original voltage

**t**is time of charging

**CR**is the time constant (C is capacitance and R is resistance)

## Time constant

The time constant is the product of the resistor and capacitor in a circuit.

It is measured in seconds

It is measured in seconds

## Working with 'e'

**e**is a constant like pi.

It is roughly 2.718281828.

On your calculator you will see a '

**ln**' and '

**e^x**' button. These stand for natural log and exponential function.

## Uses

Capacitors are used to remove the bump in the current when an a.c. current is put through a d.c. device - which only likes current in one direction