SET 3 ECT Flashcards
Current is
The movement of electrons
What is meant by the term impedance?
It is a measure of the opposition to AC current flow in a circuit
What is the name of the pressure that moves electrons in aclosed circuit?
Voltage
Batteries differ from fuel cells in that
A battery is a closed system
One coulomb passing a point in one second is one
Ampere
What does the abbreviation “RF” refer to?
Radio frequency signals of all types
A communications device that combines transmissions fromseveral I/O devices into one line is a
Multiplexer
How much power (roughly) a light emitting diode can couple intoan optical fiber?
100 microwatts
In practical applications, battery voltage
Is lowered as the load increases
What are the basic building blocks that all matter is composedof?
Electrons, neutrons, and protons
If current through a resistance is halved
The voltage is halved
Most data communications involving telegraph lines use
Narrowband channel
Which electronics material opposes the movement of freeelectrons?
Insulator
Which of the following is used to convert a radio signal from onefrequency to another?
Mixer
Which voltage source converts chemical energy to electricalenergy?
Battery
Which of the following battery types is rechargeable?
Lead-acid gel-cell
Lithium-ion ()
Nickel-metal hydride
A basic electric circuit is made up of what components?
A voltage source, a load, and a conductive path for current
How much power (roughly) a light emitting diode can couple intoan optical fiber?
100 microwatts
Primary batteries, unlike secondary batteries, may be
Used once
battery’s capacity to deliver power is measured in
Ampere hours
Which of the following condition is used to transmit two packetsover a medium at the same time?
Collision
How much power is being used in a circuit when the appliedvoltage is 13.8 volts DC and the current is 10 amperes?
138 watts
Which of the following communications lines is best suited tointeractive processing applications?
Full duplex lines
Which of the following types of channels moves data relativelyslowly?
Narrow band channel
the resistance in a circuit with constant voltage increases, thecurrent will
Decrease
A lead-acid battery is an example of a
Secondary battery
What are the three electrodes of a PNP or NPN transistor?
Emitter, base, and collector
How many digits of the DNIC (Data Network Identification Code)identify the country?
First three
A station in a network forwards incoming packets by placingthem on its shortest output queue. What routing algorithm isbeing used?
Hot potato routing
An example of potential energy is
A battery
Which part of an atom has no electrical charge?
Neutron
What do you call a diagram that shows the electrical connectionsof a circuit’s components?
A schematic diagram
If an electrical system is compared to a fluid system, theelectrical current corresponds to the
Water flow
In a synchronous modem, the digital-to-analog convertertransmits signal to the
Equilizer
What are the units of impedance?
Ohms
What is the kilowatt-hour consumption of a 40 W lamp if itremains on for 1750 h?
70
Which of the following types of channels moves data relativelyslowly?
Narrow band channel
What is the minimum number of wires needed to send data overa serial communication link layer?
2
Which of the following statement is correct?
Transmission section of a synchronous modem contains the scrambler
What is a transceiver?
A unit combining the functions of a transmitter and a receiver
Which of the following battery types is not rechargeable?
Carbon-zinc
The probability that a single bit will be in error on a typical publictelephone line using 4800 bps modem is 10 to the power -3. If noerror detection mechanism is used, the residual error rate for acommunication line using 9-bit frames is approximately equal to
0.009
Which data communication method is used to transmit the dataover a serial communication link?
full-duplex
When does maximum power transfer happen from the source tothe load?
When the source resistance equals the load resistance
The synchronous modems are more costly than theasynchronous modems because
They contain clock recovery circuits
If 60 J of energy are available for every 15 C of charge, what is
the voltage?
4 V
Frames from one LAN can be transmitted to another LAN via thedevice
Bridge
Which term describes the ability of a receiver to detect thepresence of a signal?
Sensitivity
What at are the three electrodes of a field effect transistor?
Source, gate, and drain
A secondary cell generates dc via chemical activity; a primarycell generates dc
Chemically
Which of the following precautions should be taken whenmeasuring high voltages with a voltmeter?
Ensure that the voltmeter and leads are rated for use at the voltages to be measured
