RLC
The phasor model correctly represents a circuit comprised of only an inductor and an AC generator.
A transformer is to be designed to increase the 30 kV-rms output of a generator to the transmission-line voltage of 345 kV-rms. If the primary winding has 80 turns, how many turns must the secondary have?
920
An alternating current supply is connected to a resistor through a rectifier as shown in the diagram.
Which pattern will be viewed on the screen of an oscilloscope connected across the resistor?
half wave rectification
An alternating current has a peak value of 1.75 A through a 148 Ω resistor. What is the energy dissipated by the current in a time of 365 s?
Irms=1,23A
Q=I2Rt=66,4kJ
Electrical energy is usually transmitted using alternating current. Suggest why the transmission is archived using
i) High voltages
ii) AC
i. For the same power (transmission), high voltage with low current. With low current, less energy losses in transmission cables
ii. Voltage is easily/efficiently changed
A sinusoidal alternating voltage is to be rectified.
a) Suggest one advantage of full-wave rectification as compared with half-wave rectification.
b) The rectification is produced using the circuit of Figure1.
All the diodes may be considered to be ideal. The variation with time t of the alternating voltage applied to the circuit is shown in Figure 2 and in Figure 3.
i. On the axes of Figure 2, draw a graph to show the variation with time t of the potential difference across diode A. ii. On the axes of Figure 3, draw a graph to show the variation with time t of the potential difference across diode B. c) i. On Figure 1, draw the symbol for a capacitor, connected into the circuit so as to provide smoothing.
ii. Figure 4 shows the variation with time t of the smoothed potential difference across the resistor R in Figure 1.
1. State how the amount of smoothing may be increased.
2. On Figure 4, draw the variation with time t of the potential difference across resistor R for
(a) e.g. more (output) power available e.g. less ripple for same smoothing capacitor
(b) (i) curve showing half-wave rectification (ii) similar to (i) but phase shift of 180°
(c) (i) correct symbol, connected in parallel with R
(ii) 1. larger capacitor / second capacitor in parallel with R (not increase R)
2. same peak values AND correct shape giving less ripple
The circuit contains a 3.60-mH inductor. The r.m.s. voltage of the generator is 25.0 V. Find the r.m.s. current in the circuit when the generator frequency is 1.00 x 102 Hz.
XL=2,26 Ohm
Irms=11,1A
The number of turns on the transformers is as shown in the figure. What is the output voltage of the transformers, in volts, if the input voltage of the transformers is 5 V?
30V
A bridge rectifier consists of four ideal diodes A,B, C,D connected as shown
An alternating supply is applied between the terminals X Y
fgdhs
Compute the applied voltage and impedance in a series RL circuit in which the voltage across the resistor is 50 volts, the voltage across the inductor is 120 volts, and the current is 13 milliamps.
Voltage 130 V Impedance 10 kΩ
(i) The output of the generator is connected to the primary coil of a transformer. The primary coil has 70 turns. The secondary coil has 1180 turns and is connected to power transmission cables. Calculate the RMS voltage output of the transformer.
(ii) Explain how a transformer operates.
(iii)Name the material used for the core of the transformer and explain why the core is made of this material.
(iv)Explain why a voltage in not induced at the output when a constant direct voltage is at the input.
i) 400kV
ii) mention of a magnetic field changing magnetic field emf/voltage, produced/induced/generated
iii) core of laminated iron or core of (soft) iron increases flux linkage (with secondary coil) / to reduce flux loss
IV) Voltage [accept e.m.f] (induced only) when flux (in core/coil) is changing, constant/direct voltage gives constant flux/field
Наша сестра обычно ходит в кино в субботу.
Our sister usually goes to the cinema on Saturdays.
If an R = 1-kΩ resistor, a C = 1-μF capacitor, and an L = 0.2-H inductor are connected in series with a V = 150 sin (377t) volts source, what is the maximum current delivered by the source?
𝐼𝑚=𝑈𝑚/ 𝑍
Calculates impedance
54 mA
Transformers are used in a National Electricity Distribution Grid. The diagram shows part of this National Grid.
(a) Complete the two spaces in the sentence. Transformer C is a ___________ transformer and transformer D is a .________ transformer.
(b)For the system to work the power is generated and distributed using alternating current rather than direct current. Why?
(c) Transformers are an essential part of the distribution system. Explain why.
(d) The transmission cables are suspended high above the ground. Why?
a) step-up .... step-down ... both in the correct order
b) transformers only work with a c
c) used to increase or decrease or change voltage or current reducing the energy or heat or power loss (along the cables) or reduce to safe domestic level must be consistent with first answer
d) Any 2 correct answers from: (several metres of) air gives good electrical, or insulation (between cables and earth) or reduce chance of earthing or sparks or arcing or to avoid people touching it
Мы с друзьями занимаемся английским не два раза в неделю, а четыре.
My friends and I don't study English twice a week. We study four times a week.