Capacitor
Capacitor
Capacitor
Electrolytic capacitors, plastic capacitors, base ceramic capacitors (chip capacitors) and solid capacitors.
DETAIL
The appearance and structure of capacitors vary depending on their type, and there are many different types of capacitors commonly used today. Most capacitors have at least two metal plates or conductors on metal surfaces separated by a dielectric. The conductor can be a metal foil, film, sintered metal beads or an electrolyte. Non-conductive dielectrics can increase the electrical storage capacity of capacitors. Common dielectric materials include glass, ceramics, plastic films, paper, mica and oxides. Capacitors are used in many circuits. Capacitors, unlike resistors, ideally consume no energy.
When a voltage is applied between two conductors separated by a dielectric, an electric field is created across the dielectric, so positive charges are concentrated in one conductor and negative charges in the other conductor. The capacitance of a capacitor is defined as the ratio between the accumulated charge and the voltage of the conductor. The unit of capacitance in the International System of Units (SI) is Farad (F), which is defined as 1 coulomb per volt (1 C/V). The capacitance of general capacitors is about 1 picofarad (pF) (10−12 F) to 1 milliFarad (mF) (10−3 F). The capacitance of a capacitor is directly proportional to the surface area of the conductor and inversely proportional to the distance between the conductors. In practice, the dielectric between conductors will pass a small leakage current. The electric field strength of dielectrics also has an upper limit, so the capacitor will have a breakdown voltage. The conductors in the capacitor and its pins create unwanted equivalent series inductance and equivalent series resistance.
Capacitors are commonly used in electronic circuits to block direct current and allow alternating current to flow through the capacitor. In analog filter circuits, capacitors smooth the output of a power supply. Capacitors and inductors in LC circuits can tune the radio to a specific frequency. It can stabilize the flow of voltage and power in power transmission systems. In early digital computers, the energy storage properties of capacitors were used as dynamic memory.