# Search results

1. ### What areas of study does electrical engineering cover

Not a bit but a lot, especially in Engineering Electromagnetics and in Communication Systems and in Microwave Engineering. I think there are a little chemistry in High Voltage.
2. ### Delta Power System

I don't check whether the numerical values are true or not, but there are errors in calculating the real power in the resistors. On assumption that the currents values are true. PA12 is OK. PB12 = I1 - I2 = (|(49.68A<-68.6 - 49.68A<-128.6)|^2) * 12 = something By "|" I mean the magnitude...
3. ### Engineering Finding Rth of an RLC circuit

It depends on whether you have a DC circuit or an AC circuit. 1) DC A) Since the reactance of an inductor is given by: XL = j*(2 * pi * f * L) and (f = 0) in a DC circuit, so inductor is replaced by a short circuit. ( An element with zero reactance or resistance) B) For the capacitor: Xc = 1...
4. ### Need a book suggestion

For the topics you mentioned I think the following book will be a great help: Thomas L. Floyd, Digital Fundamentals
5. ### Engineering Help with Second Order Circuits

Dear Friend di/dt = A2 * t * (-20 * e (-20t) ) + A2 * e(-20t) The derivative of multiplied terms.
6. ### Simple Voltage Problem

The output voltage is the same voltage that appears across the Diode. If we have some ideas about the voltgae across the diode we will know the output voltage. During the positive cycle the diode is reversed biased and we can replace it with an open circuit...
7. ### Finding Vc

Look at the Hint carefully. It says that you should integrate I(t) over a period of time to find the voltage. If you want to integrate you should have a function, i.e. current as a function of time. So...obtain the relation between the current and the time. Then integrate it over the desired...
8. ### Transistor biasing question.

This has error in number. 3.6 - 640 Ib - 0.7 = 0
9. ### Frequency Response/Content/stuff

GREAT. You are doing well.
10. ### Engineering Basic Circuits - Thevenin's Thm explanation

Q6/ 1) The KVL is written for a closed loop. So, choose a closed loop and go on. For the perimeter the KVL is written as it is seen in the solution. Let's Write KVL for the inner portion to see what problem we will encounter: -35 - 20 * 4 - 3 * 4 + Vcs = 0 where: Vcs is the voltage across...
11. ### Phasor Voltage and Voltage RMS value

Phasor voltage represents the instantaneous value of the voltage. For example in time t the voltage may have a value of 120V and one second later it may have a voltage of 50V. The rms voltage is (let say) the ac voltage that is equivalent to the dc voltage. This is not very clear. Isn't it...
12. ### Frequency Response/Content/stuff

Frequency Response: Is a function (in frequency domain) that shows how element properties (Admittance or Impedance for example), a current, a voltage or many other quantities in a circuit varies with frequency. Transfer Function: Is a function (in frequency domain) that relates between the...
13. ### Gain bandwidth product

Sorry for being intrude, but it is worth while to know that the dB values never should be multiplied or divided. The only allowable operation on dB quantities are addition and subtraction. Also since the GBWP units is Hz, so the Gain should be unitless (Volt/Volt).
14. ### Engineering ELEG - DC Motor Control Systems Problem

Yes, it is wrong. I attach the right SFG. Use it to obtain the transfer function and then substitue Hi/He with the given expression. I think it will work. Ω is the capital form of omega which represents the speed in radian/second. Ωm(s) is the Laplace transfor of ωm(t). This represents the...
15. ### Voltage & Resistors

OK. But afterward you should do it yourself so that you deeply understand it. Remember that you can't make muscles looking me lift weights :) . I1 = V/(R1 + R2) = 0.076 mAmp I2 = V/(R3 + R4) = 0.096 mAmp V2 = I1 * R2 = 1.368 V V4 = I2 * R4 = 2.016 V Vx = V2 - V4 = - 0.645 (It is negative...
16. ### Finding Current

Don't bother yourself. I understand. But don't be dissappointed. As soon as you practice these concepts will become very simple for you and in the future courses you will use these concepts as a tool to solve other problems. I'm sure. No. Let's advance step by step through the solution. 1)...
17. ### Voltage & Resistors

The current is splitted between the parallel resistances and they have the same voltage. In other hand R1 and R2 are in series and the same current will flow through them. The same is true for R3 and R4. The current through R1 and R2 id given by (let's call it I1) I1 = V / (R1 + R2) The...
18. ### Finding Current

At the point you pointed to it, the total current (red) is splited to two components. Ix and the other component (green). http://img246.imageshack.us/img246/7354/29346556.png [Broken] I don't understand what do you mean, but the diferrent current not always means that we have parallel...
19. ### Voltage & Resistors

OK. Great. Now, you have the series resistance values and you know the voltage across them. You should know the current. Afterward the knowledge of the voltage across each single resistor will help in finding Vx. Try it. It is easy.
20. ### Finding Current

It seems that you have some problems in distinguishing the parallel and series configuration. Two resistors are parallel if their ends are connected together or sometimes it is said that if they have the same voltage. Look at R1 and R2; you assumed that they are paralle. What do you think; are...
21. ### Non-equilibrium states in Semiconductor

Yes, but to be more specific a non-equilibrium state happens when an electron gains some kinetic energy and jumps to an energy level that is higher than its stable or eqilibrium state. The electron may gain this energy either from an external source (such as light or UV) or an internal source...
22. ### How a cascaded common emitter transistor amplifier is modelled

Exactly. Just draw the equivalent circuit of the first stage , the second stage is connected to the first stage output and go on. As vk6kro said you can calculate the gains of each stage alone and then multiply the gains, or you can deal with the circuit as a whole circuit and determin the...
23. ### Instantaneous, causal systems

I think there are some confusion in the concept of a Causal system and a Memoryless system... the two are basically different. A system is called Causal if its output y(t) at an arbitrary time t = to depends on only the input x(t) for t =< to. That is, the output of a Causal system at the...
24. ### 1/R = 1/R1+ 1/R2 - Parallel Resistors

Resistors in Rectabgle 3 are in parallel with that in rectangle 2 and the parallel combination are in series with rectangle 1: http://img34.imageshack.us/img34/1774/67916352.png [Broken] RAB = [(R + RL) // R] + R = RL = 542 SO, [(R + 542) * R / (R + R +542)] + R = 542
25. ### Voltage & Resistors

I am not well familiar with the rules, but I think you should write down your attempts so that someone can help you in solving this problem. Hint: Use Ohm's law.
26. ### Any recommendation for a book about Electromagnetic waves and radio communications

For electromagnetics: 1) William H. Hayt, Engineering electromagnetics (have articles for both undergraduate and post graduate courses) 2) David K. Cheng, Field and wave electromagnetics (chapters for both electromagnetics and microwave. Undergraduate only)
27. ### Good electronics textbooks

I tink this will be good for electronics, especially that this book emphasizes on practical work. Thomas Floyd, Electronic devices If you want a more advanced book I recommand Adel Sedra, Microelectronic circuits ( this is a universal reference book)
28. ### Average power of sinusoidal signal

The average power of the signal x(t) is given by: P = lim T ---> infinity * (1/T) * [ integration of x2(t) over (0 to T) with respect to t] please ditinguish between "T" and "t". "T" is the period of the signal and "t" is the time. If you integrate [A cos (ωt + ф)]2 over (0 to T) and...
29. ### El. Eng. ProblemCan Someone help me with it

If the steps is not clear see: http://www.allaboutcircuits.com/vol_1/chpt_10/8.html
30. ### El. Eng. ProblemCan Someone help me with it

Thevenin's theorem procedures: 1) Replace a short circuit instead of the voltage sources and open circuit instead of current sources. 2) Remove the 5 Ohm resistor that you want to calculate the current through it leaving an open circuit instead of the resistor. 3) Calculate the...