Electric fields

[Niha afzal]

I have a theory question this time ... case 1

if I have two plates and theres a potential difference (p.d) across them 250 v ... an electron is fired from one end to the other end with some speed v m/s

 

Case 2

Now I take the same plates same p.d however the plates are not uniform this time..... willl this have any effect on the speed of the electron? Compared to case 1 ... or will the time change?

[studiot]

1) What do you think the path of the electron will be in both cases?

 

2) sketch the lines of constant field strength in both cases.

 

3) What is the angle between the constant field strength contours and the Force on the electron.

 

4) What do you think this does to the path of the electron?

[foxy john]

If you were an electron wanting to get from A to B in the shortest possible time, which way would you go?

[Niha afzal]

In case 1 the electron moves In a straight line

In case two the field lines are shorter at the bottom than at the top

Force on electron is towards right the field lines also go from positive to negative I.e towards right .... but the electron is negative hence repels .. (therefore not sure about the path of electron.... it will depend on the fact which is stronger the p.d or the repulsive force by electron) maybe .

Foxy john if I were the elctron I would have chose to go.from the bottom ... lesser distance less time

[studiot]

In all cases the field strength equal the voltage divided by the plate separation E = V/d

 

But in the second case the plate separation varies, due to the geometry so this induces a second component, perpendicular to the original, as the field strength increases from bottom to top, as in the diagram.

 

This causes the electron's path to curve.

 

 

Is this really an A level question?

[Niha afzal]

This was the question .....

 

Yeah my teacher told me the path willl be curved today I know why thanks to u and special thanks for answering such a stupid question ...

[studiot]

Foxy has a point.

 

This reminds me of the following question.

 

Four circus performing fleas are placed at each corner of a 1 inch square ABCD.

At the ringmaster's whisltle all the fleas start to walk towards their neighbour.

So A walks towards B, who walks towards C who walks towards D, who walks towards A.

They all walk straight towards their target at all times.

Since they are all in motion each flea walks a spiral path and they meet in the centre.

 

How far does each flea walk?

Edited April 1, 2016 by studiot

[Niha afzal]

But I think I dnt understand the question properly. .. if the fleas walk in a straight line and its a square cube how do they meet at the center thy must just walk 1 inch... how will they meeet ( this is getting confusing:( )

[studiot]

A walks towards B.

But B is walking towards C who is walking towards.......

etc

 

So A is constantly turning inwards as he is always walking directly towards B.

 

Draw a sketch and you will see what i mean.

[Niha afzal]

Are u referring ti.something like this?

[Sensei]

In the real world experiment, it looks like this:

 

 

 

 

 

This is from my Van De Graaff generator.

Each time discharge is slightly different, but they are always from the closest as possible distances between plates. Therefor it's good to use f.e. needles. Spark will be from the end of needle.

When electrons flow through metal, they heat it. Hot metal has different resistance than cold(er) metal.

So the next time electrons choose slightly different path through metal where is lower temperature, and smaller resistance.

 

Now, sort of, parallel plates:

 

 

 

 

I choose couple frames from over 800. Spark in each discharge is in slightly different place and has different shape.

 

ps. I wanted to attach Anim GIF, but SFN didn't play it, so had to switch back to static frames.

Edited April 1, 2016 by Sensei

[Niha afzal]

Beautiful simply beautiful sensei the effort is much appreciated I can finally see what's happening here :') which made this thing much more simple:)

Edited April 2, 2016 by Niha afzal

[Sensei]

A few hundred thousands volts discharge:

[Niha afzal]

:D :D its amazing the above conversation is making sense :') the curved path thingy