# Intro to moving charges in a particle

1. Aug 16, 2007

Can anyone describe to me what happens to electrons when one material is charged negatively by rybbing it on a second material, what must be different about the materials for this to work?

And why does vinigear act as such a better electrolyte then water in a wet cell type?

Why is a complete curcuit required in order to have a continoius flow of current?

Can anyone explain the difference between conventuoional current and electron flow? why were they both developed?

2. Aug 16, 2007

### mgb_phys

Good questions - not sure how deep an answer you need (sorry I'm a Brit I don't know what age grade 11 means);

In simple terms electrons get pulled off one material and end up on the other.
One of two materials must have a strong ability to grab new electrons and the other must have weakly held electrons that can be pulled off.

Because it splits easily into oppositely charged ions which can move to carry charge through the circuit. Water although weakly charged itself doesn't split.

Because otherwise charge will build up at the ends and oppose the flow of more charge, flow of charge = current.

conventional current is a flow from positive to negative, it was decided to name it this way before electrons were discovered - it is completely arbitrary, just like putting north at the top of maps. By the tme it was discovered that electrons being negatively charged move toward positive there were too many books, laws and trained electrical engineers to change it! This happens a lot in science!

3. Aug 16, 2007

Wow thanks for answering all that lol it had the perfect answeres to my questions and i understood it too good job THANKS!

4. Aug 16, 2007

ohh i have another question... how is direct current different from alternating curent? Why do you thinkk the alternating current system was chosen in Canada?

5. Aug 16, 2007

ohh i have another question... how is direct current different from alternating curent? Why do you thinkk the alternating current system was chosen in Canada?

6. Aug 16, 2007

### mgb_phys

Direct current is a constant voltage, like a battery.
Alternating current varies in a voltage with time.

The main advantage of AC is that you can use a transformer to change the voltage very easily and efficently.
This is important because electricity flowing in wires wastes energy as heat. The higher voltage you use the less power you waste, so long distance electric wires run at upto 500,000 volts which is then converted down to 110V before reaching your house.
Also early electric motors were easier to build as AC rather than DC and originally most electricity was used to run motors in factories.

7. Aug 16, 2007

### nicktacik

In an AC system the voltage can be described by
$$V(t) = V_0 \sin{(\omega t)}$$

In a DC system the voltage is constant

Here is a good lesson
http://www.school-for-champions.com/science/ac.htm

Or try