Cannot even grasp the basics of electricity.

Hi all,

I've had a little browse through this forum and it seems I am well below even the bottom rung of knowledge when it comes to electricity so my apologies for the basic questions.

I'm just not getting to grips with electricity at all - or rather the basics of electricity - voltage, current and resistance. I've got 4 beginner books explaining it (including your own eBook and a For Dummies book), but despite pouring mountains of time over the first couple of chapters of each book thing just aren't clicking at all! The traditional analogies (water fountain, hosepipe etc.) really don't help things, I'm not sure if I'm over-thinking things or what... If I do know the material it certainly doesn't feel like it, so much so I'll read further on before I come across something that casts doubt on what I may already know.

So, if it is okay, would you mind helping me get through the basics while I'm working through your eBook again? If somebody could take a few moment to help me out with a few things below I'd really appreciate it.


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I've read over the static electricity section and although I have a rough idea, things still seem very hazy, but I understand the atomic model with the electrons, protons and neutrons quite okay. So in regards to the static electricity section:

• What are the two categories called (i.e. the category for the materials that have a positive charge and those that have a negative charge) – using positive and negative terminals doesn't make sense when dealing with glass and silk?

• Does every material in the world fall under one of the two categories? How about something that's not quite physical like air?

• Would it be correct to say that everything is a conductor, just that some materials are extremely bad at conducting so are classed as insulators, or is there an actual point where if something conducts a little above or a little low of a given limit that it is classed as a conductor or insulator?

• If I have two materials (glass and silk) and rubbed them together, I'm essentially forcing electrons from one material onto (or into?) the other, correct?

• If you walk across a carpet with the shoes on:

Thanks for your help.
Gump.

Gump said:

I've read over the static electricity section and although I have a rough idea, things still seem very hazy, but I understand the atomic model with the electrons, protons and neutrons quite okay. So in regards to the static electricity section:

• What are the two categories called (i.e. the category for the materials that have a positive charge and those that have a negative charge) – using positive and negative terminals doesn't make sense when dealing with glass and silk?

Click to expand...

Side note:, please don't use special format features, it makes responses a pain.

Some materials are sticky on their surface for electrons, while others can't hang on very well to their electrons. At this level the electrons are on the surface, as it they are "wet". This is the fundimental difference between conventional electricity and static electricity.

• Does every material in the world fall under one of the two categories? How about something that's not quite physical like air?

Click to expand...

Air generates static also. Have you read ElectroStatic Discharge?

• Would it be correct to say that everything is a conductor, just that some materials are extremely bad at conducting so are classed as insulators, or is there an actual point where if something conducts a little above or a little low of a given limit that it is classed as a conductor or insulator?

Click to expand...

Everything is not a conductor. You are right in that to some degree it is relative though. I've seen superconducting wire that uses copper and silver as insulation. When you have a perfect conductor (0 ohms) then everything else looks like an insulator. Try using Wikipedia, it will define an insulator.

• If I have two materials (glass and silk) and rubbed them together, I'm essentially forcing electrons from one material onto (or into?) the other, correct?

Click to expand...

Not into, onto. It is a surface phenomina.

• If you walk across a carpet with the shoes on:

• Why does a charge build up? Why is it not lost as soon as your shoe touches the carpet again? For example, if you rub glass and silk together, they then attract each other, but when they do the electrons on one piece of material transfer to the other causing the materials to have a neutral charge (?), why is it not the same for your shoes and the carpet?

• If rubber is an insulator and your shoes have a rubber sole, why do you still get a build up of charge?

Thanks for your help.
Gump.

Click to expand...

Static electricity is usually the result of electrons not flowing. If rubber is an insulator why would/how could the electrons move?

Hi Bill,

Thanks for the reply - I'll do my best to understand your answers...

Side note:, please don't use special format features, it makes responses a pain.

Click to expand...

My apologies, I'll note that for the future.

This is the fundamental difference between conventional electricity and static electricity.

Click to expand...

Just a quick terminology question, is it correct for me to say "a static charge on an object"?

So, static electricity is specifically talking about electrons building up on the surface of some material, whereas conventional electricity is the flow of electrons? Does this mean that if I rub some glass with silk, there is a static charge between the two objects, but if I put some conductive material between them, then does this then become conventional electricity as opposed to static?

Air generates static also. Have you read ElectroStatic Discharge?

Click to expand...

I'll have a little read if it if you think it will help at this stage. To be honest I've been following the order of your eBook very strictly.

Static electricity is usually the result of electrons not flowing.

Click to expand...

When you create a build up of static charge, is it correct to say that you are forcing a flow of electrons?

Thanks for your help.

Static is the opposite of flow, think about the root words outside the context of electricity.

Electrons act a lot like fluid, to the extent in the early days of research it was thought to be a fluid.

While it is probably a good thing to read the ebook sequentially, don't forget it is also a reference book.

When you have a spark or use a wire, you are discharging the static charge. In many ways the charge of a capacitor and a static charge are the same thing, except one is accidental and one is by design.

I wrote the ESD article, it is a how to not damage your projects. I would definitely put in put in the front of the list.

Gump, for a good read on how electricity works and the basic principles, I would suggest starting here:

http://amasci.com/ele-edu.html

These are by far the most insightful articles I have come across on the subject.

Hi Gump,
just curious, what are your plans on what to do with what you are learning?

Are you trying to learn, electrics, electronics, or the physics behind it?

I did electronics in high-school, and physics to degree level, and I can't draw an RC oscillator circuit or work out the maths without a crib sheet.

However, I can use microcontrollers to control logic circuits. Sometimes ignoring the analog issues and concentrating on an area which can be easily (and perhaps more safely) played with is a better way to learn?

I am usually all for reading and reading until a subject is learned, but with electronics, I found that experimenting was the best way of getting it in.

Perhaps, get a voltmeter, a battery, capacitor, LED, a couple of logic gates and resistors and play with the effects that can be produced.
For example, you could have the battery going through a switch, to a resistor, then to a capacitor in parallel to an LED.
Depending on the value of the resistance, the capacitor will 'soak' up the charge coming through the switch at a variable rate. Once this charge (the electrons) has saturated the capacitor, they have no-where else to go but through the LED, which would then light. The size of the resistor would effect the delay between making the switch, and the LED lighting.


For the static electricity side of things, consider the electrons as water sitting on a bench again (I know you don't like this analogy). Your hand isn't absorbant to water (well it is, but not in this case). If you put your hand onto the water and brushed it, you wouldn't soak the water up, you would just move it around, however, some of the water would stick to your hand. If you then shook your hand, this would be equivalent of increasing the accelerative force in the system (voltage is the accelerator), and the water will fly off towards (well away from) the accelerative force.

One experiment I have seen a few times which is fun, is to get a plastic rod (polythene), rub it (against hair?), and then hold it near a stream of water leaving a tap. The stream of water will be attracted towards the rod, due to the electrostatic charge left on the rod.

Penguin has a good point. Understanding the details of static electricity will never make a circuit that works. If you don't ever get it well understood, that won't stop you.

True enough, but it was where the OP started, and the beginning of his Q&A. It is useful for electronics in that it can damage most modern electronics to one extent or another.

I suspect he started reading the AAC book. I recommend simple projects along with the reading, it is a lot more fun.