If electricity is flow of electrons and also positive and negative

1. Apr 19, 2012

hackersatyam

if electricity is flow of electrons and also positive and negative charges attract
then why electricity needs a conducting medium.
electrons has mass and it should just travel through vaccum
then why in vaccum electricity cann't travel

2. Apr 19, 2012

Re: electricity

Charged particles can travel through vacuum.Examples include electrons travelling in cathode ray tubes and X- ray tubes.

3. Apr 19, 2012

rollcast

Re: electricity

Electricity is made up of a flow of electrons and electrons can flow across a vacuum. The main problem with this over a long distance is that you need a force to get the electrons to travel across the vacuum.

Old CRT achieved this by heating the cathode and then due to thermionic emission the electrons had enough energy to leave the cathode then an electric field is used to accelerate and direct the electrons towards the screen.

However in a vacuum with a small enough separation distance between the electrodes the potential difference should be enough to cause the electrons to flow.

4. Apr 19, 2012

jim hardy

Re: electricity

"Electricity" is a vague term. Probably it usually means electric charge.

I'm not sure i know what electric charge really is, exactly.

Electrons carry charge and roughly 6E18 of them carry one coulomb.

In a vacuum electrons can achieve substantial velocity.
But in a conducting medium they just bump along like people on an escalator, or like marbles in a tube.
The time delay between an electron entering near end and another exiting far end is very short, comparable to speed of light along the path. But the individual electrons move very slowly.
It's the force between them that propagates fast.

SO - train your mind to think of "charge" as something that transports energy around in a circuit,
propelled by the Electro-Motive-Force (EMF, abbreviated to E) that's encouraging charge carriers(usually electrons) to pass on their energy to the next one in line... It will save you a major readjustment of thinking later on.

You need to become fluent in both so-called "Electron Flow" and "Conventional Current Flow" because outside academia you will encounter folks who've been trained in both methods of circuit analysis. The two are completely equivalent and give the exact same Kirchoff equations.

Just remain aware that there's another world beyond circuit analysis . The simple model we use of positive or negative charged particles [STRIKE]migrating[/STRIKE] passing energy around a circuit is not the whole picture. But it will carry you a long way in your studies. And it will allow you to become competent in electronics.

I wish my maths were good enough to explain Maxwell's equations.
Let me be a little more honest here - i wish i even understood them.

Anyhow here's an interesting and not-too-techincal musing on the subject.
http://amasci.com/elect/charge1.html

old jim

Last edited: Apr 19, 2012