Inductance and Capacitance

Capacitance 

 The ability of a capacitor to store electrical charge.

Capacitor

A device that stores energy in an electric field between two plates.

Dielectric

A non-conducting material placed between capacitor plates.

Variable Capacitor

A capacitor whose capacitance can be adjusted by turning a knob.

Electrolytic Capacitor

A polarized capacitor that must be connected with correct polarity.

Non-polarized Capacitor

A capacitor that can be used in AC or DC without polarity concerns.

Plates

The two conductive surfaces inside a capacitor that hold charge.

Inductance

 The opposition to changes in current flow.

Henry (H)

Standard unit of inductance.

Millihenrys

A smaller unit of inductance commonly used for coils.

Coil

A wound conductor that produces inductance.

Electromagnetic Field

A field produced around an inductor when current flows

Inductive Reactance (XL)

The opposition to AC current caused by inductance.

Frequency (f)

 The number of AC cycles per second (Hertz).

Hertz

 Unit of frequency.

DC Voltage Effect

 The capacitor charges until capacitor voltage equals the source voltage.

DC Current Effect

 Current flows only until the capacitor is charged, then stops.

Open Circuit (DC)

when there is a break in the path, stopping current flow

Capacitor as Voltage Source

can momentarily power a circuit.

Capacitor Discharge

 Releasing stored energy when connected to a load.

AC Current Effect

 A capacitor allows AC current to pass because voltage constantly changes.

Capacitive Reactance (XC)

 Opposition to AC current caused by a capacitor.

Capacitor Safety

 Capacitors can deliver high current; discharge before working.

Bleeder Resistor

 Built-in resistor used to safely discharge large capacitors.

Total Series Inductive Reactance (Series)

 XL_T = XL1 + XL2 + XL3

Total Parallel Inductive Reactance (Parallel)

 XL_T = XL1 + XL2 + XL3

Total Parallel Inductance

 LT = 1 / (1/L1 + 1/L2 + 1/L3)

RC Time Constant (τ)

 τ = R × C (one time constant)

Full Charge/Discharge Time

 Five time constants (5τ)

Starter

 An automatic switch that closes to start a fluorescent lamp.

Ballast

 Limits current and produces high starting voltage for fluorescent lamps.

Cathodes

 Heated filaments inside a fluorescent tube.

Inductive Reactance in Ballast

 The AC property that limits current after the lamp starts.