**Capacitance**

The property of a circuit that permits the storage of an electric charge when a difference of voltage is applied.

**Current**

Electric current is the rate of flow of charge in a conductor.

**Current Limiting Resistor**

A resistor inserted into an electric circuit to limit the current to some pre-established value.

**Current Source**

A two-terminal circuit element with an output current essentially independent of the voltage between its terminals and characterized by a high internal resistance.

**Capacitor**

A capacitor is a passive device which stores energy in an electric field and opposes a change in voltage.

**Circuit**

An electric circuit is a combination of various electric circuit elements to form a closed path or loop.

**Capacitive Reactance**

Opposition to the flow of an alternating current by the capacitance of a circuit; equal to 1/2πfC and measured in ohms.

**Close Circuit**

A continuous path from the voltage source through interconnecting wiring and device(s) and back to the source.

**Continuous-Time System**

When the time variable t takes its values from the set of real numbers, the system is said to be a continuous time system or and an analog system.

**Conductance**

Conductance is defined as the reciprocal of a resistance. The unit of conductance is mho or Siemens.

**Closed-Loop Control System**

In a closed loop control system, the controller is fed by a signal that is the difference between the reference input signal and the modified output.

**Coulomb**

Electric charge is a basic property of atomic particles of matter, measured in coulombs C.

**Conductor**

Materials with many free electrons that facilitate the passage of electric current.

**Coaxial Cable**

A transmission line in which one conductor is concentric to another and separated by a continuous solid dielectric spacer.

**Corona**

A luminous discharge of electricity caused by ionization of the air around a conductor carrying a high potential.

**Circuit breaker**

An automatically operated electrical device which is designed to safeguard a circuit from damage caused by unexpected excessive electric current, generally consequent of an overloading or electric short circuit. The circuit breaker’s main purpose is to disrupt current flow after a fault in an electric system is sensed.

**Circular mil**

A unit of area equal to π/ 4 of a square mil (0.7854 square mil). The cross-sectional area of a circle in circular mils is therefore equal to the square of its diameter in mils.

**Co-energy**

A function associated with the ﬁeld energy function such that the sum of the energy and co-energy functions is equal to the sum of the products of the flux linkage of a coil multiplied by the corresponding current flowing through it.

**Complex power**

The product of the phasor voltage multiplied by the complex conjugate of the phasor current.

**Core losses**

The power dissipated in a magnetic core subjected to a time-varying magnetizing force.

**Counter emf**

The effective electromotive force within the system that opposes the passage of current in a specified direction

**Critical resistance**

The value of field circuit resistance of a DC Shunt Generator above which the generator fails to trip.

**Current divider**

A parallel circuit used to split the current amongst several branches

**CPU**

Central Processing Unit. A microprocessor system that contains the system memory and is the PLC’s decision-making unit.

**Cycle**

The positive and negative alternations of a wave.

**Current Clamp or Current Probe**

A specialized piece of electrical test equipment for measuring large currents. These currents are frequently over one amp and higher.