Hvac Module 3 Basic Electricity Flashcards
Ampere (A)
The unit of measurement for current flow: The magnitude is determined by the number of electrons passing a point at a given time
Alternation Current (AC)
An electrical current that changes direction on a cyclical basis
Current
The rate of volume at which electrons flow in a circuit, measured in amperes
Direct current (DC)
An electric current that flows in one dirction. A battery is a common source of DC voltage
Electromagnet
A coil of wire wrapped round a soft iron core. when a current flows through the coil, magnetism is created
Load
A device that converts electrical energy into another form of energy (heat mechanical motion light, etc ) Motors are the common significant loads in HVAC/R systems
Power
The amount of energy (measured in watts) consumed by an electrical load: power= Voltage times current
Rectifier
A device that converts AC voltage to DC voltage
Resistance
The opposition to the flow of electrons (i.e., load).
Transformer
Two or more coils of wire wrapped around a common core. used to raise and lower voltages.
Volt(V):
The unit of measurement for voltage
Voltage:
A measure (in volts) of the electrical potential for the current flow; also known as electromotive force (EMF).
Continuity
A continuous current path. The absence of continuity indications an open circuit
Inductive
Describes an operation where a conductor becomes electrically charged from being near another eclectically charged body, or becomes magnetized by being within an existing magnetic field. The process itself is called Induction
Insulator
A device or substance that inhibits the flow of current; the opposite of conductor
Ohms
The unit of measurement for electrical resistance
Relay
A magnetically operated device consisting of a coil and one or more sets of contacts
Thermistor
A semiconductor device that changes resister with a charge in temperature
Watts (W)
The unit of measure for power consumed by a load
Ohms law
a formula for calculation voltage current or resistance
Current letter symbol I unit of measurement Amperes (A)
Resistance letter symbol R unit of measurement OHMS
Voltage letter symbol E unit of measurement Volts (V)
TO find voltage E= I times R
TO find Current I= E divided by R
TO find Resistance R= E divided by I
Ammeter
A test instrument used to measure current flow
Analog meter
A meter that uses a needle to indicate a value on a scale
Clamp on meter
An ammeter with operable jaws that are placed around a conductor to sense the magnitude of the current flow
Digital Meter
A meter that provides a direct numerical reading of the value measured
In line ammeter
A current reading meter that is connected in series with the circuit under test
Multimeter
A test instrument capable of reading voltage current and resistance current and resistance also known as a volt ohm milliammeter (VOM)
Contactor
a control device consisting of a coil and one more sets of contacts used as a switching device in high voltage circuits
Ladder diagram
a simplified schematic diagram in which the load lines are arranged like the rungs of a ladder between vertical lines representing the voltage source
Lind Duty
a protective device connected in series with the supply voltage
Motor starter
a Magnetic switching device used to control heavy duty motors
Pilot duty
a protective device that opens the motor control circuit which then shuts off the motor
Short circuit
A situations in which a conductor bypasses the load causing a very high current flow
slow blow fuse
a fuse with a built in time delay
Solenoid coil
An electromagnetic coil used to control a mechanical device such as a valve or relay contacts
