When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is （）..

第1题

[] Which of the listed items will stop a motor due to a reduction in voltage and restart it when the voltage is restored to normal?（）

A、A.Low voltage protection circuit B、B.Non-renewable link fuse C、C.Renewable link fuse D、D.Low voltage release circuit

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第2题

[单选题] A fuse that blows often should be replaced only with a fuse of （）.

A、the recommended current and voltage rating B、higher current and voltage rating C、higher current and lower voltage rating D、lower current and higher voltage rating

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第3题

[单选题] A fuse that blows often should be replaced only with a fuse of （）.

A、the recommended current and voltage rating B、higher current and voltage rating C、higher current and lower voltage rating D、lower current and higher voltage rating

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第4题

[单选题] “380V/220V Y/△” noted on the nameplate of a non-synchronous motor means that（）

A、the armature terminals of the motor should be connected in star formation when voltage of power supply is 380 B、the armature terminals of the motor should be connected in star formation when voltage of power supply is 220 C、both A and B are correct D、the armature terminals of the motor should be connected in reverse ways of A and B

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第5题

[单选题] Possible phase relationships between voltage and current in an alternating current circuit include which of the following conditions?（）

A、Current and voltage may be in phase B、Current may lead the voltage C、Current may lag the voltage D、All of the above

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第6题

[单选题] When current and voltage reach maximum values at the same time, the power factor is（）

A、minimum B、maximum C、leading D、lagging

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第7题

[单选题] When the voltage remains constant and the resistance is increased in a series circuit, the flow of current （）

A、increases by the square of the original value B、increases C、remains the same D、decreases

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第8题

[多选题] Which of the following correctly describe steps in the OSI data encapsulation process?（）

A、The transport layer divides a data stream into segments and may add reliability and flow control information. B、The data link layer adds physical source and destination addresses and an FCS to the segment. C、Packets are created when the network layer encapsulates a frame with source and destination host addresses and protocol-related control information. D、Packets are created when the network layer adds Layer 3 addresses and control information to a segment. E、The presentation layer translates bits into voltages for transmission across the physical link.

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第9题

[多选题] Which of the following correctly describe steps in the OSI data encapsulation process?（）

A、The transport layer divides a data stream into segments and may add reliability and flow control information. B、The data link layer adds physical source and destination addresses and an FCS to the segment. C、Packets are created when the network layer encapsulates a frame with source and destination host addresses and protocol-related control information. D、Packets are created when the network layer adds Layer 3 addresses and control information to a segment. E、The presentation layer translates bits into voltages for transmission across the physical link.

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When voltage and current developed in an AC circuit reach their peak values at the same time, the power factor is （）

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