(edit: I found it was already answered here , sorry about that.)  In a Crookes Tube, electrons are accelerated from cathode to anode, and overshoots the anode in a straight line.    The question would be: Why do the electrons in this case NOT follow the shortest path from cathode to anode?
120947
I understand that Sir William Crookes'  shows that cathode rays travel in a straight path but I am unsure of why the cathode rays  aren't affected by the anode as there is an electric field and therefore bend.     Sorry if this is a silly question but I am relatively new to physic.
91514
We know for a metallic conductor   Current $\frac{I}{enA} = v$ where $v$ is drift velocity , $e$ is the charge of an electron, $n$ is no of electrons per unit volume and $A$ is area of cross section.  Ok my questions that I am struggling with:   Does it depend on length of wire? (let's say if the current is the same and area is also the same but one wire is longer and one wire is shorter then is the drift velocity for both wires the same?) Does it depend on the cross sectional area of the wire? (Yes, according to the relation, if the area is greater, drift velocity is lower, correct?)   I have digged university physics still I couldn't get my answer :( .
2369
Let's consider an infinite square well. In the first exited state there is a node at the middle of the well (i.e. wave function and thus probability of finding the particle is zero there). If I measure the position right now, I may find the particle on the left side of the node, and if I measure the particle after some time, I may find the particle on the right side of the node. But must  a particle on the left side to go to right side not pass through the node point? Thus the particle will spend some time at that point, so there should be some probability of finding the particle there, but the wave function is zero there, so what's wrong with the arguement? Does the particle move here to there, without passing through the space in between? But that will just violate continuity equation?
35228
Please be kind, I am an electronics nub.  This is in reference to getting an LED to emit photons.  From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons flow from the more negative side to the more positive side.  In an example experiment (involving a primary dry cell, a SPDT switch, a resistor and an LED) it states that the resistor MUST be connected to the anode of the LED.  In my mind, if the electrons flow from negative to positive, wouldn't the electron flow run through the LED before the resistor; thereby making the resistor pointless?
103111
In the experiments for photoelectric emission, the light is incident on one face of the emitting plate, for example the anode, when determining the stopping potential. The electrons are emitted by this face of the plate. Why are the electrons emitted in the direction of the incident light, and not opposite to it?  I have read a little about photons (the key words being, a little), and from what i gather, they have an intrinsic momentum $p=h/\lambda$, which is transferred entirely to the particle that absorbs it (along with the energy $h\nu$). This should imply that the electrons try to move further into the cathode, and not escape it! What is the fault in the reasoning?  Thanks!
24994
Electricity takes the path of least resistance!   Is this statement correct?    If so, why is it the case?  If there are two paths available, and one, for example, has a resistor, why would the current run through the other path only, and not both?
32044
this is a very short question, probably I'm missing  something really simple: according to Drude model, we have for the drift velocity of electrons, being also the average velocity: $$ v_d = \frac {-e E \tau } m  ,$$ where $ \tau$ is average free path time. Now, how can this be the average electron velocity? This velocity comes from the whole momentum increase during the free path, shouldn't we consider the average electron being only at half of the path, dividing the velocity by 2?
94542
When I learned, what the anode and the cathode are, there were two definitions corresponding to each other:   Cathode is, where electrons enter in the system. Anode comes from the greek anodos meaning "going upwards", that is where current enters the system (that is the dirrection opposing to the flow of the electrons)   Now when I tried to understand the reverse biasedness of a photodiode, I struggled half an hour until I realized, that most of the sources I could find, refers the N-doped end of the diode a cathode, even if the current is now reverse.  Did I miss something? Why is that? Is there another interpretation for these notions?
63276
I know that the question is quite stupid but I want to get an insight of this case. consider 3 resistors connected in series with a battery, after the current passes through resistor 1 it loses some of its energy, the kinetic energy of the charge carriers will definitely also decrease and so does the drift velocity then why doesn't the current decrease? Its quite confusing.
102265
The electromagnet spectrum looks to be continuous, yet energy is discrete. Shouldn't one see evidence of the electron's "quantum leap"? What's going on?     Moderator, please size my photo. Thank you.
121703
So I was recently wondering what happens to the excess charge when it is placed on an insulator or conductor e.g. rubbing two objects together. I know in the conductor the electrons are free to move whereas in the insulator they in general are not very mobile so the charge stays in a small region. But why does this happen? I know about the differences in insulator and conductor band structure, how is this related? Do the excess electrons become part of the band structure?  Thanks!
23555
We all know that the amount of current flowing b/w the plates is independent of the frequency. If I were to ask why doesn't it depend then you'd probably say that it depends on the number of electrons rather than the frequency or you might show me a current vs frequency graph.  But here is my theoretical argument. Electric current is defined as the amount of charge flowing through a point/space/wire per unit time. Let I be current due to photo electrons ejected by photons of some frequency. Now if I would increase the frequency, the kinetic energy of the ejected electron would increases, therefore it will move faster and therefore contribute more current (charge will through the same point many times per unit time) . Thereby, giving a net current greater than I.  What is wrong with my argument?  After thinking a lot, I came up with a possible reason. However fast the electrons may move, but when they hit the metal plate, they would lose their velocity and start moving in drift velocity. Now there is a problem with this argument. If this were to be true then I should expect to see a big chunk of extra electrons getting stuck at the anode.  If my reasoning was correct, then why can't I see a big charge buildup at the anode.
43459
I am starting to see a lot of people claiming that convential current is 'wrong' because Franklin made an error when he first started investigating electrostatics, and that later scientists didn't bother correcting the mistake, but preferred to keep the 'convention' (here is a classic example: )  I always thought he didn't get it wrong. He said that current is positive in the direction that positive charge flows, and vice-versa. He of course had no way to know which side of two sticks behind rubbed actually gained or lost mass. So he wasn't wrong. What were you taught?  P.S. I can't help but feel we are lucky that he got it 'backwards', because clearly many people are confused about electrostastics (including the author of that text book!) and believe electricity has to involve electrons (an unfortunate name... why couldn't they have been named negatrons...)
101859
We could imagine a simple electronic circuit composed by a power source and a resistor.   It is usual find descriptions as "The moving charged particles in an electric current are called charge carriers. In metals, one or more electrons from each atom are loosely bound to the atom, and can move freely about within the metal. These conduction electrons are the charge carriers in metal conductors." (wikipedia ). That made me imagine electrons going from power -, running by the wires, crossing the resistor and returning to power +, where they suffer a new kick to power -. All that at near the speed of light.  In this model, it is easy to define "electrical current intensity" as proportional to the number of electrons per second that cross one specific point of the circuit.  However, looking for the physics of resistivity, I can read the phrase "The actual drift velocity of electrons is very small, in the order of magnitude of a meter per hour." (wikipedia ). This is a complete different point of view, where electrons are more or less fixed around a fixed position (or moving very slowly), an electricity is a wave of "collisions" or "jumps" of electrons, like in a Newton's cradle (or "do the wave" as public in a football match). Obviously, we do not need severals hours from the switch on to the light on.  So, the question is, do electrons move around a circuit ? References to band theory are welcome.  A related question is: if electrons doesn't moves along the circuit, what is "electrical current intensity"?  Note: I known there are similar questions already posted, but answers of the ones I've read are not very detailed (could be I've not found the best ones). Please, be a few patient before "close vote".
59911
I have seen in several textbooks that say that when we connect a conductor with a battery then electrons start moving (drifting) in the battery in random up and down motion in the opposite direction of the applied electric field, the average velocity of electrons during this motion is then said to be the drift velocity , but it is also claimed that this drift velocity is constant.   Why is it so? If a constant electric field is present then why wouldn't the drift velocity just increase?
32604
Why do electrons not fully fill up all the orbitals sequentially? By this I mean: why don't the electrons fully take up the previous orbit first and then move onto the next orbit? Take calcium for example, it's electron config is 2, 8, 8, 2. Why isn't it 2, 8, 10? Why does another orbit need to be created when there are still many spots to fill up?  (I know that this is a chemistry question in a physics forum, but I really could not find a chemistry or even a broader science type forum here )
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How is it possible for current to flow so fast when charge flows so slowly?  We know electrons travel very slowly while charge travels at ~the speed of light.