题目内容

Which of the following laws explains how motors、generators and transformers work? ( )

A. Lenz’s law
B. Faraday’s law
C. Ampere’s law

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For a Y connection, the line current IL is( )

A. Equal to phase current IL=Ip
B. Equal to square root 3 times phase current IL=1.73Ip
C. Equal to phase current divided by square root three IL=Ip/1.73

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When ac current flows in a conductor, the current distribution is not uniform over the conductor cross sectional area and the current density is greatest at the surface of the conductor. This causes the ac resistance to be higher than the dc resistance. This behavior is known as ( )。

A. Corona discharge
B. Skin effect
C. Ferranti effect
D. Phase angle

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( ) is an electric discharge brought on by the ionization of a fluid/air surrounding a conductor。

A. Corona discharge
B. Skin effect
C. Ferranti effect
D. Phase angle

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A Y connected balanced impedance has value ZY=5+j30Ω. Convert this to an equivalent Δ connected impedance and the impedance ZΔ is( )。

A. 5+j30Ω.
B. 30+j5Ω.
C. 15+j90Ω

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Which of the following laws explains how motors、generators and transformers work? ( )

A. Lenz’s law B. Faraday’s law C. Ampere’s law

For a Y connection, the line current IL is( )

When ac current flows in a conductor, the current distribution is not uniform over the conductor cross sectional area and the current density is greatest at the surface of the conductor. This causes the ac resistance to be higher than the dc resistance. This behavior is known as ( )。

( ) is an electric discharge brought on by the ionization of a fluid/air surrounding a conductor。

A Y connected balanced impedance has value ZY=5+j30Ω. Convert this to an equivalent Δ connected impedance and the impedance ZΔ is( )。

A. Lenz’s law
B. Faraday’s law
C. Ampere’s law