【单选题】
三相半控桥式整流电路电阻性负载时，控制角a的移相范围是___。
A. 0~180°
B. 0~150°
C. 0~120°
D. 0~90°
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相关试题
【单选题】
三相半控桥式整流电路电阻性负载时，每个晶闸管的最大导通角6是___。
A. 150°
B. 120°
C. 90°
D. 60°
【单选题】
三相半控桥式整流电路电阻性负载，每个晶闸管电流平均值是输出电流平均值的___。
A. 1/6
B. 1/4
C. 1/2
D. 1/3
【单选题】
三相半控桥式整流电路电感性负载有续流二极管时，若控制角a为___，则晶闸管电流平均值等于续流二极管电流平均值。
A. 90°
B. 120°
C. 60°
D. 30°
【单选题】
三相半控桥式整流电路电感性负载晶闸管承受的最高电压是相电压U2的___倍
A. 根号2
B. 跟好
C. 根号6
D. 根号12
【单选题】
三相半控桥式整流电路电感性负载，每个品闸管电流平均值是输出电流平均值的___。
A. 1/6
B. 1/4
C. 1/2
D. 1/3
【单选题】
三相半控桥式整流电路电感性负载，每个二极管电流平均值是输出电流平均值的___。
A. 1/4
B. 1/3
C. 1/2
D. 1/6
【单选题】
三相全控桥式整流电路由三只共阴极___与三只共阳极晶闸管组成。
A. 场效应管
B. 二极管
C. 晶闸管
D. 品体管
【单选题】
三相全控桥式整流电路是由一组共阴极的三相半波整流可控整流电路与另一组共阳极的三相半波可控整流电路相___构成的。
【单选题】
三相全控桥式整流电路电阻负载，控制角a增大，输出电压___
【单选题】
三相全控桥式整流电路电阻负载，电流连续与断续的分界点是控制角a=___
A. 30°
B. 60°
C. 90°
D. 120°
【单选题】
三相全控桥式整流电路电感性负载无续流管，晶闸管电流有效值是输出电流平均值的___倍。
A. 1.414
B. 1.732
C. 0.707
D. 0.577
【单选题】
三相全控桥式整流电路电感性负载有续流管，控制角a的移相范围是___。
A. 0-30°
B. 0-60°
C. 0-90°
D. 0-120°
【单选题】
三相全控桥式整流电路电感性负载无续流管，控制角a大于___时，输出出现负压。
A. 90°
B. 60°
C. 45°
D. 30°
【单选题】
三相半波可控整流电路电感性负载无续流管，输出电压平均值的计算公式是___
A. Ud=1.17U2cosα(0°≤α≤30°)
B. Ud=1.17U2cosα(0°≤α≤60°)
C. Ud=1.17U2cosα(0°≤α≤90°)
D. Ud=1.17U2cosα(0°≤α≤120°)
【单选题】
三相全控桥式整流电路电感性负载无续流管，输出电压平均值的计算公式是___
A. Ud=2.34U2cosα(0°≤α≤30°)
B. Ud=2.34U2cosα(0°≤α≤60°)
C. Ud=2.34U2cosα(0°≤α≤90°)
D. Ud=2.34U2cosα(0°≤α≤120°)
【单选题】
三相可控整流触发电路调试时，首先要检查三相同步电压波形，再检查___，最后检查输出双脉冲的波形。
A. 整流变压器的输出波形
B. 同步变压器的输出波形
C. 三相锯齿波波形
D. 晶闸管两端的电压波形
【单选题】
三相可控整流触发电路调试时，要使每相输出的两个窄脉冲(双脉冲)之间相差___。
A. 60°
B. 120°
C. 90°
D. 180°
【单选题】
单相半波可控整流电路电阻性负载的输出电压波形中一个周期内出现___个波峰。
【单选题】
单相桥式可控整流电路电阻性负载的输出电压波形中一个周期内会出现___个波峰。
【单选题】
单相桥式可控整流电路电感性负载无续流管，控制角a=30°时，输出电压波形中___。
A. 不会出现最大值部分
B. 会出现平直电压部分
C. 不会出现负电压部分
D. 会出现负电压部分
【单选题】
单相桥式可控整流电路电阻性负载的输出电流波形___。
A. 只有正弦波的正半周部分
B. 正电流部分大于负电流部分
C. 与输出电压被形相似
D. 是一条近似水平线
【单选题】
单相桥式可控整流电路大电感负载无续流管的输出电流波形___。
A. 始终在横坐标的下方
B. 始终在横坐标的上方
C. 会出现负电流部分
D. 正电流部分大于负电流部分
【单选题】
三相半波可控整流电路电阻性负载的输出电压波形在控制角___时出现断续。
A. a>45°
B. a>30°
C. a>90°
D. a>60°
【单选题】
三相半波可控整流电路电阻性负载的输出电压波形在控制角___的范围内连续。
A. 0<a<30°
B. 0<a<45°
C. 0<<60°
D. 0<a<90°
【单选题】
三相半波可控整流电路电感性负载的输出电流波形___。
A. 控制角α>30°时出现断续
B. 正电流部分大于负电流部分
C. 与输出电压波形相似
D. 是一条近似的水平线
【单选题】
三相半波可控整流电路电感性负载无续流管的输出电压波形在控制角___时出现负电压部分。
A. g>60°
B. Q>45°
C. a>30°
D. a>90°
【单选题】
三相半波可控整流电路电感性负载，控制角a增大时，输出电流波形___。
【单选题】
三相半波可控整流电路电阻性负载的输出电流波形在控制角a<___时连续。
A. 60°
B. 30°
C. 45。
D. 90°
【单选题】
三相半波可控整流电路电阻性负载，每个晶闸管电流平均值是输出电流平均值的___。
A. 13
B. 1/2
C. 1/6
D. 1/4
【单选题】
三相桥式整流电路电阻性负载的输出电压波形在控制角a>___时出现断续。
A. 30°
B. 60°
C. 45°
D. 50°
【单选题】
三相桥式可控整流电路电感性负载，控制角a增大时，输出电流被形___。
【单选题】
三相桥式可控整流电路电阻性负载的输出电流波形，在控制角a<___时连续。
A. 90
B. 80°
C. 70°
D. 60°
【单选题】
426三相桥式可控整流电路电阻性负载的输出电流波形，在控制角a>___时出现断续。
【单选题】
三相桥式可挖整流电路电感性负载无续流管的输出电压波形，在控制角a>___时会出现负电压部分。
A. 20°
B. 30°
C. 45°
D. 60°
【单选题】
马制管触发电路所产生的触发脉冲信号必须要___。
A. 与主电路同步
B. 有一定电抗
C. 有一定电位
D. 有一定频率
【单选题】
晶闸管触发电路发出触发脉冲的时刻是由___来定位的，由偏置电压来调整初始相位，由控制电压来实现移相。
A. 脉冲电压
B. 触发电压
C. 异步电压
D. 同步电压
【单选题】
晶闸管触发电路发出触发脉冲的时刻是由同步电压来定位的，由___来调整初始相位，由控制电压来实现移相。
A. 脉冲电压
B. 触发电压
C. 偏置电压
D. 异步电压
【单选题】
KCO4集成触发电路由锯齿波形成、___、脉冲形成及整形放大输出等环节组成。
A. 三角波控制
B. 移相控制
C. 方波控制
D. 偏置角形成
【单选题】
KCO4集成触发电路中11脚和12脚上所接的R8、C2决定输出脉冲的___。
【单选题】
KCO4集成触发电路在3脚与4脚之间的外接电容器Cl上形成___。
A. 正弦波
B. 三角波
C. 锯齿波
D. 方波
推荐试题
【单选题】
___属于人工智能的应用。
A. ：程序设计
B. ：指纹识别
C. ：社区聊天
D. ：数据统计
【单选题】
)，并了解他们考虑的一些问题。这些问题一般不包括___。
A. ：他们对将要讨论的事项了解多少
B. ：他们需要什么，又想要知道什么
C. ：他们的艺术水平和欣赏能力如何
D. ：他们将如何利用分析展示的信息
【单选题】
信息处理技术员资格考试的试卷包括信息处理基础知识、计算机基础知识、法律法规知识、专业英语、办公软件使用技能五个方面。某次考试后，对这五个方面分别统计了各考生的得分率以及全国的平均得分率。为了直观展现每个考生在各个方面的水平以及该考生的整体水平，并与全国平均水平进行比较，宜采用___。
A. ：直方图
B. ：圆饼图
C. ：折线图
D. ：雷达图
【单选题】
The___ is the primary device for entering information into the computer
A. ：disk
B. ：printer
C. ：keyboard
D. ：memory
【单选题】
___ system let you run more tlian one program at a time
A. : Application
B. :Software
C. : Real time
D. :Multitask
【单选题】
Small business may use___ for word processing
A. : microcomputers
B. :industrial computers
C. : mainframe computers
D. :supercomputers
【单选题】
Once you've made the Internet connection, you can send___ to any of computer user all around the w orld
A. ：e-mail
B. :WWW
C. ：ccc
D. ：web station
【单选题】
Which statement about zone-based firewall configuration is true？___
A. You can assign an interface to more than one zone
B. Traffic is implicitly denied by de fault between interfaces in the same zone
C. The zone must be configured before it can be a ssigned
D. Traffic that is destined to or sourced from the Self zone is de nied by default
【单选题】
Refer to the exhibit line in this configuration prevents the help Desk user from modifying the interface configuration.___
A. Privilege exec level 10 interface
B. Privilege exec level 9 configure terminal
C. Privilege exec level 7 show start-up
D. Username HelpDesk privilege 6 password help
【单选题】
You have been tasked with blocking user access to websites that violate company policy， but the sites use dynamic IP addresses. What is the best practice for URl filtering to solve the problem？___
A. Enable URL filtering and use URL categorization to block the we bsites that violate company
B. Enable URL filtering and create a blacklist to block the websites that violate company policy
C. Enable URL filtering and create a whitelist to block the websites that violate company policy
D.
E. nable URL filtering and use URL categorization to allow only the websites that company policy allows users to access.
【单选题】
Within an 802. 1x-enabled network with the auth Fail feature configured， when does a switch port get placed into a restricted VLAN？___
A. When a conected client fails to authenticate after a certain number of attempts.
B. if a connected client does not support 802. 1x
C. when AAA new-model is ena bled
D. after a connected client exceeds a specified idle time
E. when 802. 1x is not globally enabled on the Cisco Catalyst switch
【单选题】
Which type of attack does a proxy firewall protect against ？___
A. cross-site scripting attack
B. worm traffic
C. port scanning
D. DDoS attacks
【单选题】
When an administrator initiates a device wipe command from the ISE， what is the immediate effect？___
A. It requests the administrator to choose between erasing all device data or only managed corporate data.
B. It requests the administrator to enter the device pin or password before proceeding with the operation
C. It notifies the device user and proceeds with the erase operation
D. It immediately erases all data on the device
【单选题】
What is a valid implicit permit rule for traffic that is traversing the ASa firewall？___
A. ARPs in both directions are permitted in transparent mode only
B. Unicast IPv4 traffic from a higher security interface to a lower security interface is permittee in routed mode only.
C. Unicast IPv6 traffic from a higher security interface to a lower security interface is permitted in transparent mode only.
D. Only BPDUs from a higher security interface to a lower secur ity interface are permitted in transparent mode.
E. Only BPDUs from a higher security interface to a lower secur ity interface are permitted in routed mode
【单选题】
A specific URL has been identified as containing malware. What action can you take to block users from accidentally visiting the URl and becoming infected with malware ？___
A. Enable URL filtering on the perimeter router and add the URls you want to block to the router's local URL list
B. Enable URL filtering on the perimeter firewall and add the URls you want to allow to the router's local URL list.
C. Enable URL filtering on the perimeter router and add the URls you want to allow to the firewall's local URL list
D. Create a blacklist that contains the URl you want to block and activate the blacklist on the perimeter rout
E. Create a whitelist that contains the URLs you want to allow and activate the whitelist on the perimeter router.
【单选题】
How does PEAP protect the EAP exchange ？___
A. It encrypts the exchange using the server certificate
B. It encrypts the exchange using the client certificate
C. It validates the server-supplied certificate,and then encrypts the exchange using the client certificate
D. It validates the client-supplied certificate,and then encrypts the excha nge using the server certificate
【单选题】
Which feature of the Cisco Email Security Appliance can mitigate the impact of snowshoe spam and sophisticated phishing attacks？___
A. contextual analysis
B. holistic understanding of threats
C. graymail management and filtering
D. signature-based IPS
【单选题】
Refer to the exhibit【nat (inside,outside)dunamic interface】 Which translation technique does this configuration result in？___
A. DynamIc PAT
B. Dynamic NAT
C. Twice NAT
D. Static NAT
【单选题】
Refer to the exhibit which are repre sents the data center？___
【单选题】
While trouble shooting site-to-site VPN， you issued the show crypto isakmp sa command. What does the given output show？___
A. IKE Phase 1 main mode was created on 10.1.1.5， but it failed to negotiate with 10.10 10.2
B. IKE Phase 1 main mode has successfully negotiated between 10.1.1.5 and 10.10..
C. IKE Phase 1 aggressive mode was created on 10.1.1.5， but it failed to negotiate with
【单选题】
Refer to the exhibit All ports on switch 1 have a primary vLan of 300 Which devices can host 1 reach？___
A. host 2
B. server
C. host 4
D. other devices within VLAN303
【单选题】
Which option is the cloud-based security service from Cisco the provides URL filtering， web browsing content security， and roaming user protection？___
A. Cloud Web service
B. Cloud Advanced Malware Protection
C. Cloud We b Security
D. Cloud Web Protection
【单选题】
How can you detect a false negative on an IPS？___
A. View the alert on the ips
B. Review the ips log
C. Review the is console
D. Use a third- party system to perform penetration testing.
E. Use a third- party to audit the next generation firewall rules
【单选题】
If a switch port goes directly into a blocked state only when a superior BPDU is received， what mechanism must be in use？___
A. STP BPDU guard
B. Loop guard
C. EtherChannel guard
D. STP Root guard
【单选题】
what improvement does EAP-FASTv2 provide over EAP-FAST？ ___
A. It allows multiple credentials to be passed in a single EAP exchange.
B. It supports more secure encryption protocols
C. It allows faster authentication by using fewer packets.
D. It addresses security vulnerabilities found in the original protocol
【单选题】
When users login to the Client less Ssl Vpn using https://209.165.201.2/test ,which group policy will be applied？___
A. test
B. clientless
C. sales
D. DfitGrp Policy
E. Default RAGroup
F. Default WEB VPN
G. roup
【单选题】
Which user authentication method is used when users login to the Clientless SSLVPN portal using https://209.165.201.2/test？___
A. AAA with LOCAL database
B. AAA with RADIUS server
C. Certificate
D. :Both Certificate and aaa with LoCAL database
E. Both Certificate and AAA with RADIUS server
【单选题】
What' s the technology that you can use to prevent non malicious program to runin the computer that is disconnected from the network？___
A. Firewall
B. Sofware Antivirus
C. Network IPS
D. Host IPS
【单选题】
Which statement about the communication between interfaces on the same security level is true？___
A. Interfaces on the same security level require additional configuration to permit interinterface communication
B. Configuring interfaces on the same security level can cause asymmetric routing
C. All traffic is allowed by default between interfaces on the same security level
D. You can configure only one interface on a n individual security level
【单选题】
Which product can be used to provide application layer protection for tcp port 25 traffic？___
A. ESA
B. CWS
C. WSA
D. ASA
【单选题】
which iPS mode is less secure than other options but allows optimal network through put ?___
A. inline mode
B. inline-bypass mode
C. transparent mode
D. Promiscuous mode
【单选题】
Which feature of the Cisco Email security Appliance can mitigate the impact of snowshoe spam and sophisticated phishing attack？___
A. reputation based filtering
B. signature based IPS
C. contextual analysis
D. graymail management and filtering
【单选题】
Which type of social-engineering attack uses normal tele phone service as the attack vector？___
A. smishing
B. dialing
C. phishing
D. vishing
【单选题】
Which quantifiable item should you consider when you organization adopts new technologies？___
A. exploits
B. vulnerability
C. threat
D. Risk
【单选题】
Referencing the ClA model， in which scenario is a hash- only function most appropriate ？___
A. securing data at rest
B. securing real-time traffic
C. securing data in files
D. securing wireless transmissions
【单选题】
Which ports must be open between a aaa server and a microsoft server to permit Active Directory authentications？___
A. 445 and 389
B. 888 and 3389
C. 636 and 4445
D. 363 and 983
【单选题】
Refer to the exhibit for which reason is the tunnel unable to pass traffic___
A. the tunnel is failing to receive traffic from the remote peer
B. the local peer is unable to encrypt the traffic
C. the ip address of the remote peer is incorrect
D. UDP port 500 is blocked
【单选题】
Which type of attack can exploit design flaws in the implementation of an application without___
A. DHCP starvation attacks
B. low-rate dos attacks
C. application DDos flood attacks
D. application DDoS flood attacks
E. volume-based DDoS attacks
【单选题】
How can you protect CDP from reconnaissance attacks？___
A. Enable dynamic ARP inspection on all untrusted ports.
B. Enable dot1x on all ports that are connected to other switches.
C.
D. isable CDP on ports connected to endpoints.
【单选题】
Which type of attack can exploit design flaws in the implementation of an application without ？___
A. DHCP starvation attacks
B. low-rate dos attacks
C. application DDos flood attacks
D. application DDoS flood attacks
E. volume-based DDoS attacks
