A: reflection
B: SWR
C: VSWR
D: match
举一反三
- The voltage meter and current meter on the main switchboard shows ( <br/>). A: phase voltage and phase current of generator B: line voltage and line current of generator C: line voltage and line current of crane D: line voltage and line current of shore power
- The plus (+) and minus (-) signs in an electric circuit diagram are used to define . A: . voltage polarity B: . current direction C: . power flow D: . absorbed power
- The function of direct current regulated power supply is to input an alternating current power of 220volts, so that it can output __________.( ) A: alternating current 200 volts voltage B: direct current 24 volts voltage C: direct current 200 volts voltage D: alternating current 24 volts voltage
- A transistor is a ( )operated device. A: voltage B: current C: both voltage and current D: none of the above
- The<br/>common-base amplifier has _()()()__. A: voltage gain, current gain, and power gain B: voltage gain and power gain, but no current gain C: current gain and power gain, but no voltage gain D: current gain and voltage gain, but no power gain
内容
- 0
The isolating switch model is GN2-10/1000, meaning ( ). A: Rated voltage 2KV, rated current 10A B: Rated voltage 2KV, rated current 1000A C: Rated voltage 10KV, rated current 1KA D: Rated voltage 10KV, rated current 10KA
- 1
The effective value of ac voltage or current is（ ） A: The average value of a voltage or current B: DC equal to the AC thermal effect is defined as the effective value of AC C: voltage or current are 0.707 of their amplitudes D: closely related to the frequency of alternating current
- 2
Which one does not belong to the advantages of power electronic devices? A: When the device turns off, it can withstand high terminal voltage and the leakage current is approximately zero B: When the device turns on, it can carry a large current, and the terminal voltage is approximately zero C: The device can work in amplified state D: The current can only flow through in one direction
- 3
The inductor voltage phase lags its current by 90 o, and the capacitor current lags its voltage by 90 o, is this conclusion true? [ ]. A: It's impossible. B: When the capacitance and inductance are nonlinear components. C: When inductance current and voltage, capacitance current and voltage are not related direction. D: Whenever.
- 4
In the free space, the magnetic strength of the magnetic field of infinite plane current (excluding the thickness of the plane current) is [img=14x24]1803b72d2d865c9.png[/img]=______. A: μ0i, whose direction is the same as the current B: μ0i/2, whose direction is the same as the current C: μ0i, whose direction is perpendicular to the current D: μ0i/2, whose direction is perpendicular to the current