Lamp Capacitor, a device that functions as a very small battery inside a circuit. At it’s most basic, a capacitor consists of two sheets of metal separated by a thin insulating sheet called the dielectric. A small bit of electricity is stored in the metal sheets when a voltage is applied across the capacitor. When the voltage is lowered, the capacitor discharges its stored electricity. Capacitors are some of the most useful electronic components and are used in everything in computer memory to automotive ignition.
(A) Flourescent lamp (B) Flourescent capacitor
A fluorescent lamp is a tricky thing to control. It has electrodes at either end and works by sending current through a gas between those electrodes. When the lamp first turns on, the gas is resistant to electricity. Once the electricity starts to flow, however, the resistance rapidly drops, making the current flow quicker and quicker. If nothing were done to control the speed of the current, so much electricity would flow through that it would heat up the gas too much cause the bulb to explode.
The ballast controls the current flowing through the valve, and the Capacitor makes the ballast more efficient.
Out of Phase
Electricity has two measurements: voltage and amperage — also known as current. The voltage is a measure of how hard the electricity is pushing, and the amperage is a measure of how much electricity is flowing through the circuit. In an efficient AC circuit, voltage and current are in phase — they increase and decrease together. When the voltage pushes into the ballast, however, the ballast initially resists the increase in current. This causes the current to lag behind the voltage, making the circuit inefficient. The capacitor is there to make the circuit more effecient by bringging the two back in phase....