Unit 2: Physical layer - Practice Quiz

1 Which type of signal varies continuously over time?

2 Which values are commonly used to represent a binary digital signal?

3 What is the number of signal cycles completed in one second called?

4 What does the amplitude of a signal generally indicate?

5 What is the basic unit of data rate?

6 A data rate of is commonly equal to how many bits per second?

7 Which term describes the maximum data-carrying capacity of a communication channel?

8 What is the loss of signal strength during transmission called?

9 Which transmission impairment is caused by unwanted electrical or electromagnetic energy?

10 What occurs when different parts of a signal change shape during transmission?

11 Which guided medium consists of two insulated copper wires twisted together?

12 Which transmission medium carries data using pulses of light?

13 Which guided medium has a central conductor surrounded by insulation and a metallic shield?

14 Which guided medium is most resistant to electromagnetic interference?

15 Which transmission medium sends signals through free space without using a physical cable?

16 Which unguided medium is commonly used for Wi-Fi communication?

17 Which unguided medium generally requires a line-of-sight path between antennas?

18 Which networking device connects different networks and forwards packets between them?

19 Which device regenerates a weakened signal so that it can travel farther?

20 Which device forwards Ethernet frames to the appropriate port using MAC addresses?

21 A periodic analog signal has a frequency of . What is its time period?

22 A digital signal has a bit duration of . What is its bit rate?

23 A composite periodic signal contains frequency components at , , and . What is its fundamental frequency?

24 A noiseless channel has a bandwidth of and uses four signal levels. According to the Nyquist formula, what is its maximum data rate?

25 A channel has a bandwidth of and a linear signal-to-noise ratio of . What is its Shannon capacity?

26 A modem transmits at baud using 16 distinct signal states. What is the resulting data rate?

27 What minimum bandwidth is required for a noiseless binary channel to carry according to the Nyquist formula?

28 A cable receives of signal power and delivers . What is the attenuation loss?

29 A transmission path contains an amplifier with a gain of followed by sections causing losses of and . What is the net gain or loss?

30 A composite signal changes shape because its frequency components experience different delays while traveling through a cable. Which impairment is occurring?

31 The signal power is and the noise power is . What is the signal-to-noise ratio in decibels?

32 Why does increasing the number of twists per unit length generally improve a twisted-pair cable's resistance to interference?

33 A company needs a copper medium with better shielding and higher bandwidth than ordinary unshielded twisted pair. Which medium is most suitable?

34 A campus needs a high-speed backbone between buildings containing heavy electrical machinery. Which transmission medium is most appropriate?

35 A broadcaster needs signals to reach receivers in many directions without precisely aligning their antennas. Which wireless medium is most suitable?

36 Two buildings use a terrestrial microwave link. A new tall structure is built directly between their antennas. What is the most likely result?

37 A geostationary satellite is approximately above Earth. Ignoring processing delay, what is the approximate one-way propagation delay from one ground station to another through the satellite?

38 A long digital cable link produces weakened and distorted pulses. Which device should be placed along the link to reconstruct and retransmit the bits?

39 A LAN administrator wants to forward Ethernet frames only to the port associated with the destination MAC address. Which device should be used?

40 Two networks use different IP address ranges and must exchange packets through the best available path. Which device performs this function?

41 A composite periodic signal is given by . What are its fundamental period and absolute bandwidth?

42 A binary signal transmits the repeating sequence at using ideal rectangular polar NRZ pulses. Which statement about its spectrum is correct?

43 An analog source band-limited to is sampled at a rate above the Nyquist minimum and quantized into levels. Ignoring framing and coding overhead, what PCM bit rate results?

44 A noiseless signaling scheme with levels is used on a channel whose measured SNR is . Considering both Nyquist and Shannon limits, what is the maximum theoretical data rate?

45 A channel must carry using signal levels at an SNR of . What is the minimum bandwidth satisfying both the Nyquist and Shannon constraints?

46 A system delivers of user data, applies B/B block coding, and then uses NRZI with one signal element per encoded bit. Under ideal Nyquist signaling, what are the signal rate and minimum baseband bandwidth?

47 A signal traverses of cable with attenuation , two connectors losing each, and an amplifier providing gain. What is the approximate output power?

48 At a receiver, the desired signal power is . Independent thermal, intermodulation, and crosstalk noise powers are , , and , respectively. What is the total SNR in decibels?

49 A channel has nearly constant amplitude response across the signal band, but its phase response is nonlinear with frequency. Which impairment and corrective action best match this condition?

50 Two equal-amplitude sinusoidal components traverse a channel. One component experiences a delay of and the other . If their frequency separation is , what phenomenon is most directly indicated?

51 An optical fiber has a bandwidth-distance product of . For a link using ideal binary NRZ signaling, what is the approximate Nyquist-limited bit rate?

52 A step-index fiber has core refractive index and cladding index . Assuming air outside the fiber, what is its approximate acceptance half-angle?

53 A coaxial cable is terminated by a purely resistive load. What are the load reflection coefficient and the corresponding return loss?

54 A balanced twisted-pair receiver has a common-mode rejection ratio of , defined using voltage ratios. If external interference induces equally on both conductors, what residual differential interference is expected ideally?

55 In a free-space radio link with unchanged antenna gains and transmit power, the carrier frequency is halved while the separation distance is doubled. According to the Friis equation, how does received power change?

56 Using the standard effective-Earth-radius approximation, the radio horizon in kilometers is , with heights in meters. What is the maximum line-of-sight distance for antennas at and ?

57 Two ground stations communicate through a geostationary satellite directly overhead, at an altitude of . Ignoring processing and atmospheric delay, what is the minimum one-way ground-to-ground propagation delay?

58 A parabolic antenna retains the same physical aperture area and efficiency while its operating frequency is doubled. Ideally, how does its power gain change?

59 Two legacy Ethernet hubs, each serving eight hosts, connect to two different ports of one Layer 2 switch. No VLANs or routers are configured. How many collision domains and broadcast domains exist?

60 A Layer 2 switch has twelve hosts connected on separate full-duplex access ports. Six hosts belong to VLAN 10 and six to VLAN 20, with no routing configured. How many collision domains and broadcast domains are present?