# Search results

1. ### Remote Internet voting security flaw?

Hi guys, Traditional voting via paper ballots at polling stations, meant that each individual was free to vote for his candidate in complete privacy. A father could vote for a separate candidate and a son for another candidate. So I was wondering is there any way in which to ensure similar...
2. ### Protocols insecure against Replay Attack

Homework Statement Determine which of the following protocols are insecure against replay attack , and explain why: (a) A → B : username, password (b) A → B : username, h(timestamp, password) (c) A → B : username, timestamp, h(password) (d) A → B : username...
3. ### Measuring the size of a molecule

Hi, Homework Statement I am trying to determine the size of a molecule..by doing the oil drop experiment where we drop a tiny droplet of oil on water covered with a thin layer of powder...and then make calculations based on the diameter of the circle... the droplet forms in oil. The Attempt...
4. ### Measuring speed of sound in air

The signal generator + loud speaker would produce audio waves. But right now the lab does not have a loud speaker. So ill have to make do without
5. ### Measuring speed of sound in air

Ok. Thanks never the less.
6. ### Measuring speed of sound in air

im stumped :confused:
7. ### Measuring speed of sound in air

ohh i thought u meant without using any microphone... So i place the mic a distance x from two people who themselves are a distance y between them. Then I ask them to both clap at the same time. and record the distance between the peaks shown on the Oscilloscope? However, I change x or do I...
8. ### Measuring speed of sound in air

Umm...but wont i still need something to catch the sound wave the 'claps' produce? :confused:
9. ### Measuring speed of sound in air

two people who clap at the same time?
10. ### Measuring speed of sound in air

which is ? :confused:
11. ### Measuring speed of sound in air

So what you are saying is; I connect the microphone to the pre amp. That will amplify the sound waves from the 'clap' and then i monitor the output from the scope? Hmm..i guess i can clap at increasing or decreasing distances from the mic ?
12. ### Measuring speed of sound in air

nope i didnt use the preamp. but how would i use the preamp just for a clap?
13. ### Measuring speed of sound in air

i tried a simple one by connecting two microphones to the oscilloscope keeping a distance x between them and clapping a distance y from both of them. But none of my claps, or any music that i played registered any wave fluctuation
14. ### Measuring speed of sound in air

Yes. The lab sheet just says we have to use a microphone and an oscilliscope. Everything else is dependent on the person doing the experiment
15. ### Measuring speed of sound in air

Hi. I have been given the task to measure the speed of sound in air. The materials available are: 1. Microphone 2. Signal Generator 3. Amplifier 4. Digital Oscilloscope I have looked through google and the simplest exp involves a loudspeaker as well. However I dont have one...
16. ### Newtons third law of motion

Homework Statement A particle of mass 4kg is being towed at a constant speed up a rough plane inclined at 30 degrees to the horizontal by a force 4g N acting parallel to the slope. At the top of the slope the particle moves onto a rough horizontal slope with the same coefficient of friction...
17. ### A doubt about RC circuits

yes...this is what i was asking. What exactly do we mean by displacement current and in Which direction would the displacement current flow?
18. ### A doubt about RC circuits

Thank you for all the help :) Ok I was actually working on this question (attached below) We have to find the current through the resistor R11 after the switch is opened. ( it was shut for a long time prior to it opening at t=0) Everything is correct but my final answer is wrong...
19. ### A doubt about RC circuits

http://apricot.polyu.edu.hk/~lam/cp/img/rc-circuit.gif" [Broken] Uhh...so what you are saying is the current goes from the +Vc towards +Vb in anti clockwise direction? But it wont go from +Vc to -Vc to -Vb to +Vb and so on in a clockwise direction?
20. ### A doubt about RC circuits

Happy new year too you too :) What did u mean by currents have to go the long way around? Anyway eventually i agree that there will be no current across a capacitor. But what about while its charging? there will be voltage across it, and shouldnt that mean a current also flows?
21. ### A doubt about RC circuits

In an RC circuit shown below, with the switch closed after a long time, when the capacitor is charging, there is a current across the capacitor given by Initial current x e ^ (-t/RC)... Is this current....the current supplied by capacitor to the rest of circuit, or simply the current across...
22. ### Engineering Solving an RC circuit question using Superposition

Yungman I made a mistake above. The current due to the capacitor is 16.666 eLaTeX Code: ^{-t/120} not - 16.666 eLaTeX Code: ^{-t/120}. However in the book instead of adding the current....they are subtracting them. This is what i dont get since both currents ( current due to the 8V voltage...
23. ### Engineering Solving an RC circuit question using Superposition

Hello, The circuit attached below is from Richard Dorfs Intro to Electric Circuits book. The switch is shut for a long time and opened at t=0. The question asks to find the i(t) across R11, which they use nodal analaysis and find it to be 66.67 - 16.666 e^{-t/120} micro Amps, where 66.67 micro...
24. ### Complex Numbers: Finding the least value of |z-w|

Ok by drawing a picture the shortest distance between Z and W is coming out too be\sqrt{}74-\sqrt{}13-3=1.9996 I did this by calculating W by \sqrt{}74- 1 and Z by \sqrt{}13 + 2, then subtracted the distance W from Z to get its smallest value. I would be greatly obliged if someone can...
25. ### Complex Numbers: Finding the least value of |z-w|

Thanks!! Although i would like to find a simpler way to do it as well.
26. ### Complex Numbers: Finding the least value of |z-w|

hmm..I get this part. You are saying that Z and W lie on the circumference of the circle with center 3,2 and radius 2 and center 7,5 with radius 1 right? I cannot get beyond this point. The question is asking for the minimum value of |z-w| so this means that both Z and W should be at maximum...
27. ### Complex Numbers: Finding the least value of |z-w|

Do u mean it will be |3+2i - ( 7+5i)|?? but that gives the answer 5 while it is 2 in the book
28. ### Complex Numbers: Finding the least value of |z-w|

Could you kindly explain this a little bit: I first get |z| by using |z|<= 2+|3+2i| and then put z= 2+|3+2i| in the formula for |z| that u have given?
29. ### Complex Numbers: Finding the least value of |z-w|

Homework Statement The complex numbers, z and w satisfy the inequalities |z-3-2i|<=2 and |w-7-5i|<=1 Find the least possible value of |z-w| Homework Equations No clue at all. The Attempt at a Solution Since its |z-w| i figured that the least possible value will only be...
30. ### Two Parallel Voltage sources and KVL

Hi, I understand that you cannot apply KVL to voltage sources connected in parallel, unless both voltage sources are the same, as this violates KVL. However, I want to know why? Just a simple 2-3 line explanation will suffice. Regards