# Search results

1. ### I Density of States Derivation

I was looking for a derivation for the density of states and I came across this page: https://ecee.colorado.edu/~bart/book/book/chapter2/ch2_4.htm I followed the derivation and came up with: g(E) = (1/L3)dN/dE = (1/L3)L3/∏2*k2 * dk/dE =K2/∏2 * dk/dE =K2/∏2 * g(E) =...
2. ### Spark in relay contacts

Why is there a spark in the relay contacts? Suppose that the coil and the contacts are connected to two different power supplies. If i suddenly disconnect the power supply to the coil, then the voltage across the coil will increase and a spark will jump across the switch that I used to...
3. ### Admissions How to pay for Masters in the US

I am a US citizen. I was born in New York but I grew up in the Philippines. I am planning to take my Masters in Electrical Engineering specializing in IC design or Control Systems in the US, but when I checked the tuition/fees I learned that it would take a crazy amount of time to save up that...

I have recently passed the Electronics Engineering Licensure exam in the philippines and I'm plannning to pursue a career in chip design preferrably mixed signal or digital. I have applied at different semiconductor companies. The problem is they don't design the IC's here, they only conduct...
5. ### Why does vacuum have resistance?

Suppose that there is a positively charged particle and a negatively charged particle in free space. The electric field of the positive charge causes a difference in potential between the position of the negatively charged particle and the positively charged particle. This, causes the negatively...
6. ### Amplitude modulation and amplifier efficiency

" A intelligence signal is amplified by a 80% efficient amplifier before being combined with a 12kW carrier to generate the AM signal. if it is desired to operate at 100% modulation, what is the DC input power at the modulator" The choices are a: 12kW b. 7.14kW c.7.5kW d. 15kW my solution...
7. ### How is a memristor different from a resistor

I read that the memristor is described by the equation dφ=Mdq. If both sides are divided by dt, then dφ/dt=Mdq/dt. But dφ/dt=V and dq/dt=I. Then V=MI which is ohm's law. Isn't the constant M just the same as resistance?
8. ### Problem with Minimum Nyquist bandwidth formula and m-ary encoding

I am using the book Electronic Communication Systems by Wayne Tomasi: I had a problem with a certain part of the book: The book gives the formula for the minimum nyquist bandwidth as: " The minimum theoretical bandwidth necessary to propagate a signal is called the minimum Nyquist bandwidth...
9. ### How do i find the principal form of this complex number

z= (10-j+elogj)2 I tried expanding but it just made it more complicated. help please!!
10. ### Effects of dc beta(hfe) in BJT characteristics

I need help in answering the post lab questions given to us by our professor. 1. Is dc beta constant on every point of the characteristics? What is its effect in the linearity of the transistor? 2. What is the effect of a high dc beta on the characteristic curves? I have attached an...
11. ### Vector analysis textbook

Can you suggest me a book in vector analysis which covers spherical and cylindrical coordinates. My professor discusses the calculation of volume, surface area and curve length, by integrating differential surface and volume elements in terms of cartesian, spherical and cylindrical coordinates...
12. ### How to use a rocker switch with three or four terminals

I've watched this youtube video : , and understood it only a little so i came here for help. How does that three terminal rocker switch work. It says that the terminals are for power, ground and acc.(Is acc accessory which means load??) If for example, i want the switch to control a simple...
13. ### Help Input output characteristics of BJT

help!! Input output characteristics of BJT I have attached an image of the graph. Does this graph apply for both npn and pnp transistors. I have asked this because for pnp, the collector(c) and base(B) terminals must be reverse-biased at the active region, and B must be at a higher potential...
14. ### Formula for ripple factor in filter circuits

i have come across two different formulas for ripple factor: One is r= (Vrpp/Vdc), where Vdc is the dc voltage of the output and Vrpp is the peak to peak ripple voltage. My professor uses this formula and I have also seen it being used in basic electronics by Floyd Another one is r= Vrms/Vdc...
15. ### Why is current constant in a series connection? AND fluid flow in pipe

My physics book explains that this is because of the conservation of charge and the fact that charge doesn't accumulate at a certain point. Can someone please explain this in detail, especially the part where it says that charge can't accumulate. Another question which i think is similar is...
16. ### Clipper Clamper book recommendation

I'm currently using Electronic devices and circuits by boylestad. My problem is that there aren't much examples about clippers and clampers, and it only uses ideal diodes and there is only one diode per circuit. Is there any book which has a good chapter about those devices. It should contain...
17. ### Clipper circuit: Sign of output voltage

I have attached the image of the clipper circuit below. When Vin is positive the diode is reverse biased and the output and input are at the same loop. When Vin is negative the diode is forward biased and Vo=0. My problem is finding the sign of the output, although I know that Vo and Vin are...
18. ### Question about the sign of output voltage in clipper circuits

I have attached an image of a clipper circuit below. First Question: When the sinusoidal input is positive or negative, how do i know how to label it in the
19. ### Is resistance of a silicon diode constant?

In our experiment we measured the forward resistance of a diode using a multimeter. We used that value and the voltage across the diode to compute the current passing through the diode. Is that value really constant??
20. ### Question about potential difference in circuit with resistance

Sorry for this post, but im desperate for an answer. Please reply thanks in advance Consider a simple circuit composed of a battery whose ends are connected by a wire. The potential difference of the battery is Vbatt ohm's law gives: V=IR If the resistance of the circuit is ignored then the...
21. ### Why is the electric field strong in sharp points?

Why is the electric field strong in sharp points?? There is a question in my book regarding the intensity of the electric field near a sharp surface in a conductor. There is a hint which says that it will be helpful to examine the field lines near those sharp surfaces. This is from my...
22. ### Help in semiconductors: minority and majority carriers!

I am currently taking up a course in electronic devices and circuits. Our first topic was about semiconductors and I'm having trouble understanding the doping process. We didn't have any prerequisite solid state course or any other course related to it that's why my professor explains the...
23. ### Electric flux through a closed surface

[EDITED] Why is the electric flux through a closed surface zero? My book based the reasoning from a uniform electric field. I understand that for a uniform electric field, the electric field doesn't diminish in magnitude as we move away from the source, and if we construct a box-shaped closed...
24. ### Total and directional derivatives:

The total derivative of the function z=f(x,y) with respect to x is: dz/dx = ∂z/∂x + (∂z/∂y)(dy/dx) The way i see this is that the total derivative, dz/dx, gives the rate of change of z with x, allowing y to vary with x at the rate dy/dx. I don't know if this is right. The directional...
25. ### Directional and partial derivatives help please

Directional and partial derivatives help please!! I have read that the partial derivative of a function z=f(x,y) :∂z/∂x, ∂z/∂y at the point (xo,yo,zo)are just the tangent lines at (xo,yo,zo) along the planes y=yo and x=xo. Directional derivatives were explained to be derivatives at a particular...
26. ### How fast is air blown from a propeller.

Let's say that we have a simple propeller, which consists only of two flat blades which is inclined at an angle of ∅ with its plane of revolution. Given, the rpm and the length of the blades, is it possible to calculate how fast air is going to be thrown back?
27. ### What really happens when charging a capacitor?

What really happens when charging a capacitor?? Do the charges move from plate to plate or do the charges in the wire only move towards the plates----> "During charging electrons flow from the negative terminal of the power supply to one plate of the capacitor and from the other plate to the...
28. ### Potential difference of capacitor in circuit

I'm having a problem with this although I just finished the chapter about electric potential and potential energy in University physics by young and freedman and I need to understand this because the next chapter is about capacitors and dielectrics and there is an example just like this...
29. ### Why is the electric field inside a hollow conductor zero?

Homework Statement The electric field is zero within the conductor because the charges are all at rest in an electrostatic situation. But the electric field inside a cavity within the conductor is not necessarily zero because it isn't part of the conductor, as my book says. Then i encountered...
30. ### HELP proof that a=v^2/r in NON-uniform circular motion

HELP!!!proof that a=v^2/r in NON-uniform circular motion Most of the proofs I have read especially the geometric approach assume that the speed is constant, so it mustn't apply for non-uniform circular motion. Some proofs use calculus and starts from the position vector and differentiates it to...