capacitor A passive electronic-circuit component
consisting of, in basic form, two metal electrodes
or plates separated by a dielectric (insulator).
capacitor amplifier See DIELECTRIC AMPLIFIER.
capacitor antenna See CONDENSER ANTENNA.
capacitor bank A network of capacitors connected
in combination, yielding a desired characteristic.
capacitor braking The connection of a capacitor to
the winding of a motor after the removal of power,
to speed up the process of braking.
capacitor color code See COLOR CODE.
capacitor decade See DECADE CAPACITOR.
capacitor-discharge ignition CAPACITIVEDISCHARGE
IGNITION.
capacitor filter In a direct-current power supply, a
filter consisting simply of a capacitor connected
in parallel with the rectifier output.
capacitor-input filter A filter whose input component is a capacitor. The capacitor-input powersupply filter is distinguished by its relatively high dc output voltage, but somewhat poorer voltage regulation, compared with the CHOKE-INPUT FILTER.
capacitor leakage Direct current flowing through the dielectric of a capacitor. In a good nonelectrolytic
capacitor, this current is normally less than 1microampere. In an electrolytic capacitor,it can be up to several milliamperes, depending on the capacitance and the applied voltage.
capacitor loudspeaker See ELECTROSTATIC
SPEAKER.
capacitor microphone See CONDENSER MICROPHONE.
capacitor motor An ac motor that uses a capacitor in series with an auxiliary field winding for starting purposes. Initially out-of-phase current in the auxiliary field (starting winding) causes a rotating field that turns the rotor. When the rotor reaches a safe speed, a centrifugal switch disconnects the capacitor and auxiliary field, and the motor continues running as an induction motor.
capacitor series resistance The ohmic loss in a capacitor. It results partly from conductor losses, and partly from losses in the dielectric material.
capacitor substitution box An enclosed assortment of selected-value capacitors arranged to be switched one at a time to a pair of terminals. In troubleshooting and circuit development, any of several useful fixed capacitance values can be
thus obtained.
capacitor voltage
1. The voltage at the terminals of a capacitor.
2. The maximum voltage rating of a capacitor.
capacitor voltmeter See ELECTROSTATIC VOLTMETER.
cap 1. Abbreviation of CAPACITANCE. 2. Abbreviation of CAPACITOR
capacitance Symbol, C. Unit, farad. The property exhibited by two conductors separated by a dielectric, whereby an electric charge becomes stored between the conductors. Capacitance is thought of as analogous to mechanical elasticity.Also see FARAD.
capacitance bridge A four-arm ac bridge for gauging capacitance against a standard capacitor. In its simplest form, it has a standard capacitor in one arm and resistors in the other three
capacitance coupling The transfer of ac energy between two circuits or devices by a capacitor or capacitance effect. Also see COUPLING.
capacitance diode See VARACTOR.
capacitance divider An alternating-current voltage divider that uses capacitors, rather than resistors. It is used in certain oscillators, such as the Colpitts type.
capacitance filter A filter consisting of only a high-capacitance capacitor. Because the capacitor cannot discharge instantaneously, it tends to maintain its voltage and smooth out the ripples in the voltage applied to it.
capacitance-inductance bridge A combination ac bridge that can be used for either capacitance or inductance measurement. Both capacitance and inductance can be measured in terms of a standard
capacitance; however, some of these bridges use standard inductors in the inductancemeasuring mode.
capacitance meter A direct-reading meter for measuring capacitance. In most available types, a stable ac voltage is applied to the meter circuit, to which an unknown capacitor is connected in series;
meter deflection is roughly proportional to
the reactance of the capacitor. Also called MICROFARAD
METER.
capacitance ratio In a variable capacitor, the ratio of maximum to minimum capacitance.
capacitance relay A relay circuit that operates from a small change in its own capacitance. It consists of an RF oscillator whose tank capacitance is very low. When a finger is brought near the circuit’s short pickup antenna, the attendant increase in capacitance detunes the oscillator, activating the relay. Also called PROXIMITY RELAY and PROXIMITY SWITCH.
capacitance-resistance bridge A combination ac bridge that can be used for either capacitance or resistance measurement. The unknown resistance is measured against a standard resistor;
the unknown capacitance against a standard capacitor.
capacitive amplifier See DIELECTRIC AMPLIFIER.
capacitive attenuator An ac attenuator whose elements are capacitors in any desired combination of fixed and/or variable units. The desired attenuation is afforded by the capacitance ratio.
capacitive coupling A means of coupling between
circuits that uses a series capacitor for directcurrent
blocking. The signal passes through the
capacitor, but the blocking effect allows different
bias voltages to be applied to the two stages.
capacitive diaphragm A metal plate deliberately placed in a waveguide to introduce capacitive reactance and, thereby, cancel an inductive reactance.
capacitive-discharge ignition An electronic ignition system for automotive engines. Provides nearly constant high voltage, regardless of engine speed. A dc-to-dc step-up converter charges a
large capacitor (typically to 300 volts) when the distributor breaker points are closed; when they are open, the capacitor discharges through the ignition coil, thereby generating an ignition pulse
of several thousand volts.
capacitive division Reduction of an ac voltage by a capacitive voltage divider.
capacitive feedback Feeding energy back from the output to the input of an amplifier or oscillator through a capacitor.
capacitive-input filter A smoothing filter for ac power supplies, in which the element closest to the rectifier is a capacitor, regardless of the components or circuits placed subsequently.
capacitive load A load consisting of a capacitor or a predominantly capacitive circuit.
capacitive loading In an antenna, the addition of capacitance in series with the element(s). This raises the resonant frequency for a radiator having a given physical length. It can also serve to increase
the physical length required for a radiator having a specified resonant frequency. Compare INDUCTIVE LOADING.
capacitive post A protrusion inside a waveguide for the purpose of introducing capacitive reactance to cancel an inductive reactance.
capacitive potentiometer See CAPACITIVE VOLTAGE
DIVIDER.
capacitive pressure sensor A pressure sensor
that uses a radio-frequency oscillator and a pair
of metal plates separated by dielectric foam. The
circuit is designed so a change in the capacitance
between the plates causes the oscillator frequency
to change. This change is sensed. A signal
is sent to an analog-to-digital converter (ADC)
and then to a microcomputer that calculates the
extent of the pressure.
capacitive proximity sensor A transducer used in mobile robots that detects the presence of certain
kinds of objects. It consists of an oscillator whose
frequency is determined by an inductancecapacitance
(LC) circuit to which a metal plate
is connected. When a conducting or partially conducting
object comes near the plate, the mutual capacitance changes the oscillator frequency. This change is detected and sent to the robot controller.
capacitive reactance Symbol, XC. Unit, ohm. The reactance exhibited by an ideal capacitor, considered as a negative pure-imaginary quantity; XC = –j/(6.28fC), where f is the frequency in
hertz, C is the capacitance in farads, and j is the unit imaginary number (the square root of –1). Alternatively, f can be specified in megahertz and C in microfarads. In a pure capacitive reactance,
current leads voltage by 90 degrees. Also see CAPACITANCE, CAPACITOR, and REACTANCE.
capacitive speaker See ELECTROSTATIC SPEAKER.
capacitive transducer A transducer consisting essentially of a refined variable capacitor whose value is varied by a quantity under test, such as pressure, temperature, liquid level, etc.
capacitive tuning Variable-capacitor tuning of a circuit.
capacitive voltage divider A capacitive attenuator usually consisting of two series-connected capacitors whose values are such that an applied ac voltage is divided across them in the desired ratio.
capacitive welding An electronic welding system in which energy stored in a capacitor is discharged through the joint to be welded. This develops the heat necessary for the operation.
capacitive window A pair of capacitive diaphragms used in a waveguide to introduce capacitive reactance.
consisting of, in basic form, two metal electrodes
or plates separated by a dielectric (insulator).
capacitor amplifier See DIELECTRIC AMPLIFIER.
capacitor antenna See CONDENSER ANTENNA.
capacitor bank A network of capacitors connected
in combination, yielding a desired characteristic.
capacitor braking The connection of a capacitor to
the winding of a motor after the removal of power,
to speed up the process of braking.
capacitor color code See COLOR CODE.
capacitor decade See DECADE CAPACITOR.
capacitor-discharge ignition CAPACITIVEDISCHARGE
IGNITION.
capacitor filter In a direct-current power supply, a
filter consisting simply of a capacitor connected
in parallel with the rectifier output.
capacitor-input filter A filter whose input component is a capacitor. The capacitor-input powersupply filter is distinguished by its relatively high dc output voltage, but somewhat poorer voltage regulation, compared with the CHOKE-INPUT FILTER.
capacitor leakage Direct current flowing through the dielectric of a capacitor. In a good nonelectrolytic
capacitor, this current is normally less than 1microampere. In an electrolytic capacitor,it can be up to several milliamperes, depending on the capacitance and the applied voltage.
capacitor loudspeaker See ELECTROSTATIC
SPEAKER.
capacitor microphone See CONDENSER MICROPHONE.
capacitor motor An ac motor that uses a capacitor in series with an auxiliary field winding for starting purposes. Initially out-of-phase current in the auxiliary field (starting winding) causes a rotating field that turns the rotor. When the rotor reaches a safe speed, a centrifugal switch disconnects the capacitor and auxiliary field, and the motor continues running as an induction motor.
capacitor series resistance The ohmic loss in a capacitor. It results partly from conductor losses, and partly from losses in the dielectric material.
capacitor substitution box An enclosed assortment of selected-value capacitors arranged to be switched one at a time to a pair of terminals. In troubleshooting and circuit development, any of several useful fixed capacitance values can be
thus obtained.
capacitor voltage
1. The voltage at the terminals of a capacitor.
2. The maximum voltage rating of a capacitor.
capacitor voltmeter See ELECTROSTATIC VOLTMETER.
cap 1. Abbreviation of CAPACITANCE. 2. Abbreviation of CAPACITOR
capacitance Symbol, C. Unit, farad. The property exhibited by two conductors separated by a dielectric, whereby an electric charge becomes stored between the conductors. Capacitance is thought of as analogous to mechanical elasticity.Also see FARAD.
capacitance bridge A four-arm ac bridge for gauging capacitance against a standard capacitor. In its simplest form, it has a standard capacitor in one arm and resistors in the other three
capacitance coupling The transfer of ac energy between two circuits or devices by a capacitor or capacitance effect. Also see COUPLING.
capacitance diode See VARACTOR.
capacitance divider An alternating-current voltage divider that uses capacitors, rather than resistors. It is used in certain oscillators, such as the Colpitts type.
capacitance filter A filter consisting of only a high-capacitance capacitor. Because the capacitor cannot discharge instantaneously, it tends to maintain its voltage and smooth out the ripples in the voltage applied to it.
capacitance-inductance bridge A combination ac bridge that can be used for either capacitance or inductance measurement. Both capacitance and inductance can be measured in terms of a standard
capacitance; however, some of these bridges use standard inductors in the inductancemeasuring mode.
capacitance meter A direct-reading meter for measuring capacitance. In most available types, a stable ac voltage is applied to the meter circuit, to which an unknown capacitor is connected in series;
meter deflection is roughly proportional to
the reactance of the capacitor. Also called MICROFARAD
METER.
capacitance ratio In a variable capacitor, the ratio of maximum to minimum capacitance.
capacitance relay A relay circuit that operates from a small change in its own capacitance. It consists of an RF oscillator whose tank capacitance is very low. When a finger is brought near the circuit’s short pickup antenna, the attendant increase in capacitance detunes the oscillator, activating the relay. Also called PROXIMITY RELAY and PROXIMITY SWITCH.
capacitance-resistance bridge A combination ac bridge that can be used for either capacitance or resistance measurement. The unknown resistance is measured against a standard resistor;
the unknown capacitance against a standard capacitor.
capacitance sensor See CAPACITANCE TRANSDUCER.
capacitive amplifier See DIELECTRIC AMPLIFIER.
capacitive coupling A means of coupling betweencircuits that uses a series capacitor for directcurrent
blocking. The signal passes through the
capacitor, but the blocking effect allows different
bias voltages to be applied to the two stages.
capacitive diaphragm A metal plate deliberately placed in a waveguide to introduce capacitive reactance and, thereby, cancel an inductive reactance.
capacitive-discharge ignition An electronic ignition system for automotive engines. Provides nearly constant high voltage, regardless of engine speed. A dc-to-dc step-up converter charges a
large capacitor (typically to 300 volts) when the distributor breaker points are closed; when they are open, the capacitor discharges through the ignition coil, thereby generating an ignition pulse
of several thousand volts.
capacitive division Reduction of an ac voltage by a capacitive voltage divider.
capacitive feedback Feeding energy back from the output to the input of an amplifier or oscillator through a capacitor.
capacitive-input filter A smoothing filter for ac power supplies, in which the element closest to the rectifier is a capacitor, regardless of the components or circuits placed subsequently.
capacitive load A load consisting of a capacitor or a predominantly capacitive circuit.
capacitive loading In an antenna, the addition of capacitance in series with the element(s). This raises the resonant frequency for a radiator having a given physical length. It can also serve to increase
the physical length required for a radiator having a specified resonant frequency. Compare INDUCTIVE LOADING.
capacitive post A protrusion inside a waveguide for the purpose of introducing capacitive reactance to cancel an inductive reactance.
capacitive potentiometer See CAPACITIVE VOLTAGE
DIVIDER.
that uses a radio-frequency oscillator and a pair
of metal plates separated by dielectric foam. The
circuit is designed so a change in the capacitance
between the plates causes the oscillator frequency
to change. This change is sensed. A signal
is sent to an analog-to-digital converter (ADC)
and then to a microcomputer that calculates the
extent of the pressure.
capacitive proximity sensor A transducer used in mobile robots that detects the presence of certain
kinds of objects. It consists of an oscillator whosefrequency is determined by an inductancecapacitance
(LC) circuit to which a metal plate
is connected. When a conducting or partially conducting
object comes near the plate, the mutual capacitance changes the oscillator frequency. This change is detected and sent to the robot controller.
capacitive reactance Symbol, XC. Unit, ohm. The reactance exhibited by an ideal capacitor, considered as a negative pure-imaginary quantity; XC = –j/(6.28fC), where f is the frequency in
hertz, C is the capacitance in farads, and j is the unit imaginary number (the square root of –1). Alternatively, f can be specified in megahertz and C in microfarads. In a pure capacitive reactance,
current leads voltage by 90 degrees. Also see CAPACITANCE, CAPACITOR, and REACTANCE.
capacitive speaker See ELECTROSTATIC SPEAKER.
capacitive transducer A transducer consisting essentially of a refined variable capacitor whose value is varied by a quantity under test, such as pressure, temperature, liquid level, etc.
capacitive tuning Variable-capacitor tuning of a circuit.
capacitive voltage divider A capacitive attenuator usually consisting of two series-connected capacitors whose values are such that an applied ac voltage is divided across them in the desired ratio.
capacitive welding An electronic welding system in which energy stored in a capacitor is discharged through the joint to be welded. This develops the heat necessary for the operation.
capacitive window A pair of capacitive diaphragms used in a waveguide to introduce capacitive reactance.
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