Thefigureshowsfourcircuits.Answerthefollowingquestions.When,thecircuitsrepresentthecharacteristicofopencircuitareshowninFig______.

As the circuit shown in the figure, the line voltage of balanced three phase source is U˙AB=380∠30oV and the impedances are Z1=50+j50Ω，ZA=ZB=ZC=50+j100Ω 问答题

As the circuit shown in the following figure, the initial energy stored in capacitor is zero and the controlled voltage source is current-controlled voltage source. S is switched from a to b at t=0. Solve: (1)When t＝4.5s, the capacitor voltage uC=[填空1]V; (2) When t＝4.5s, the current i1=[填空2]mA.

单选题

If a device is driven by current signal, what is the ideal value of its input resistance?

问答题

(Simulation) The balanced bridge is also quite useful in control systems. Let us take the temperature control system as an example. Suppose we have a thermistor whose resistance R is in direct proportion to the environment temperature. That means when the temperature increase ΔT centidegree, the resistance of the thermistor will raise ΔR ohm accordingly. The V in the circle in the following Figure is a voltmeter with very large resistance. It is clear that the voltmeter will have zero value when ΔR=0.

If the environmental temperature causes the thermistor changing its resistance to R+ΔR, the bridge is not balanced anymore. Deduce the expression of voltmeter’s voltage, find the voltage using any of your simulation software, and fill in the blank uV=[填空1]mV with uS=10V, R=10kΩ, and ΔR=10Ω:

问答题

For the one-port sub-circuit, the average value of voltage u=[填空1]V, the rms value of voltage u=[填空2]V, the average value of current i=[填空3]A, the rms value of current i=[填空4]A, and the average absorbed power of the one-port is =[填空5]W.