mahela007

whoops... I forgot my chemistry classes.

I just don't understand what anode rays are, how they are made or where they come from.. Any help will be greatly appreciated. The Wikipedia article is a stub and many others simply state that anode rays "occur".

sorry to be so persistent .... but how do electrons "stick" to oil?

That would be a positive ion right? The whole problem occurred to me when I was reading about Millikans famous oil drop experiment. I read that he used X-Rays to charge some of the oil drops.. (they way I understood it the oil drops got a negative charge.. ) So how could the X-rays give the oil droplets a negative charge?

How can X-Rays ionize air? (or other molecules)

well, I just leaned the answer on this thread so I'll try to explain the answer to your first question. If there were many, many air molecules (normal or high pressure) inside the tube, then the electrons would simple smash into them and the electrons would not be able to travel easily to the other end of the tube. Imagine that you are an electron and you are driving in your car on a road... if there was a traffic jam (the cars jamed together would be like air molecules at high pressure) you wouldn't be able to find a way through to keep travelling.You would constantly be bumping into other cars. (OOPS!) If the other cars were magically sucked out into space (Just like the air molecules are sucked out to create low pressure) then you'd have a nice, fast, pleasant drive.. Hope that helps (To [insane_alien] ...) (Was my analogy correct?)

Could someone please tell me what the definition of a coulomb is? and also what's the definition of the ampere? All the resources on the internet go in circles. Some say that the ampere is the flow of current at the rate of 1 coulomb per second. Others say that 1 coulomb is the charge per second in a wire which carries a current of 1 ampere.. These two definition are basically the same and they go in an endless circle... One wouldn't be able to define either one without the other..... So can someone please tell me the correct definition of the coulomb?

but that doesn't agree with this observation "In 1838, Michael Faraday passed a current through a rarefied air filled glass tube and noticed a strange light arc with its beginning at the cathode (negative electrode) and its end almost at the anode (positive electrode). In 1857, German physicist and glassblower Heinrich Geissler sucked even more air out with an improved pump, to a pressure of around 10-3 atm and found that, instead of an arc, the glow filled the tub"- wikipedia Why did Geissler, even with a much lower pressure , see the whole tube illuminate? With less molecules of air shouldn't the tube have become darker? Ok.. I found the answer Via IRC

Why do cathode rays illuminate the tube in which they are present? Also why do they stop giving out light at VERY low pressures?

so was I..

Thanks for your reply.. great analogy by the way.

Thanks.. Even to me, the thing about the emission wavelengths sounded a bit far fetched.... but I'm still at an introductory level of physics so I had to clarify.. thanks again!

What is the currently used definition of the meter? (meter, as in the unit of measuring length..) Someone told me that, if wavelengths of all the emission frequencies of an atom were added together the total length would be a meter. Is that true? I haven't found any reference to that definition anywhere else...

Why should the gas inside a cathode ray tube be a low pressure in order for the current to flow? (i.e the cathode rays) Why don't the rays appear when there is a gas at normal pressure inside the tube?

thanks guys...

Say an object A changes it's velocity from -3 ms-1 to 0 ms-1. Commons sense suggests that this is a decelleration because the speed of the object is decreasing. However if this motion is drawn on a velocity time graph then the gradient will be positive. A positive gradient means acceleration... (correct me if i'm wrong anywhere above).. So we knows it's a decelleration but the graph says it's an acceleration.. how can you account for this discrepancy?

Is this attraction significant enough to cause a visible deviation in the path of electrons? It appears that the electrons (i.e the spark ) travel in a straight line.

that hasn't been given in the question. I'm asked simply to state the displacement... Would that generally mean "from the reference point" or "from the initial position"?

An object is situated 10m ahead of the reference point. It starts moving in the negative direction (towards the reference point) and then continues until it reaches a point 5m behind the reference point. What is the displacement of the object? Here's my answer. The displacement is the difference between the initial and final positions of the object. As the initial position was 10m ahead of the reference point and the final position was 5m behind the reference point the total displacement would be 15m. However everyone else I ask (Except my teacher.. I haven't asked him yet) says that the displacement is 5 because it is only 5m behind the reference point.. Which answer is correct? 15 or 5? I've included a (rather crude) diagram of the problem. A is the initial position. A' is the final position and O is the reference point. The object moves from A to A'. A____________________O________A' <-------------10m----------------><-----5m-->

According to the first two images of this wikipedia article http://en.wikipedia.org/wiki/Crookes_tube the anode of the crookes tube is situated ahead of the metal cross. Why do the electrons, which come out of the cathode, continue toward the cross to form an image behind it instead of heading straight for the +ve anode? Merged post follows: Consecutive posts merged29 views and no replies... Doesn't anyone know?

Thank you VERY much!

I've tried to learn the rules for drawing the lewis structures (otherwise knows as dot-cross structures) of molecules but there are a few problems.. First of all in some instances the octet simply cannot be completed and in others there are more than 8 electrons in the outer shell. If I encounter an unfamiliar molecule how should I set about drawing the lewis structure? Secondly, I ran into a few problems with the SO4^ 2- molecule.. Why is it that the "correct" structure is a central S atom with single bonds to two O atoms and double bonds to the other two O atoms like this? O | O=S=O | O and why isn't it this.. O || O=S=O || O Both the structures seem to be correct according to the octet rule.. I even tried using the "formal charge" but even that is the same for both molecules (correct me if I'm wrong.. .I'm not very comfortable with all this yet..) Thanks in advance

thanks!

Going back to my initial question.. could you describe what happen to the kinetic energy when a solid metal ball collides with a ball of putty and the putty deforms?

Thanks for all your replies. I think I understand why momentum is conserved now.