A small electric shock

[Primarygun]

I hope this thread is put correctly.

When I stand on an insulator and touch a charged objects (Van der Graff generator) , why I can't feel a shock?

On the other hand, if I stand on the floor, I could feel the shock.Why?

Would there be any difference if the object is an electric toy car which is "leaking" electricity?

 

I wonder if the " complete circuit" plays an important role for

When I stand on an insulator and touch a charged objects (Van der Graff generator) , why I can't feel a shock? On the other hand, if I stand on the floor, I could feel the shock.Why?

[5614]

You are correct it is to do with a "complete circuit" because when you stand on an insulator the electrons cannot flow through you to the floor, whereas if you are touching the floor or another person who is touching the floor then electrons will flow through you and you will feel it.

[Primarygun]

stand on an insulator the electrons cannot flow through you to the floo

Ya, but the charge should be shared between the object and me, why there is not shock?

[5614]

Because the electrons are not flowing through you.

 

An electric shock is what you feel when a current is generated going through you, this doesn't happen in this case. Sure there's a static charge on you, that's why your hair stands up on end, but that's not the same as a flowing electrical current.

[Primarygun]

but that's not the same as a flowing electrical current.

What do you mean?

Does it mean the rate of transferring electron through my body by a current is much higher than the rate by sharing of charge?

[5614]

If you are grounded there is an electrical current ie. electrons flowing into, through and out of your body.

 

If you are insulated then electrons are transferred to you and it is static electricity.

 

The difference is that between a current and static electricity.

[YT2095]

a circuit needs 2 poles + and -

 

when you`re on the insulator and touch the charged aparatus, you simply become part of the aparatus, still with no where to go, you become just as negatively charged, but there`s still no positive to work against, so you`re safe.

 

remove the insulator and stand on the floor, your feet now have a positive charge (compartively) and so NOW you have both + and - poles.

 

you get a shock!

[Primarygun]

If you are insulated then electrons are transferred to you and it is static electricity.

Thanks YT and 5614

In both cases, electrons move in our body at a higher speed than usual.

But,by sharing, we have a net gain of charge : Being passing through by an current, we get no net charge.

Why the latter gives us a deadly but the former does not hurt us?

[5614]

Because our bodies cannot withstand an electrical current... I read once that 0.5A will kill a person, now obviously we have a mega resistance meaning you'd need a mega voltage to supply that 0.5A, but still.

[Primarygun]

What sets up the magnitude of ampere? the flow of electrons?

[YT2095]

the way I like to picture it is, Voltage is the Speed and the Amps are the Weight behind it.

 

maybe oversimplistic, but it helps with Mental Experiments

[5614]

Yes. The current is the rate of flow of electrons... the more electrons passing a point per unit of time the higher the current is.

 

When there's a high resistance a high voltage is needed to supply the 'push' on the current againt the strong resistance, which we can see in the equation V=IR (aka Ohm's law).

[5614]

Woa... one sec YT!

 

Current is the rate of flow of electrons.

 

Voltage is the potential difference, the energy, the push making the electrons move.

[Primarygun]

Current is the rate of flow of electrons.

so when we share the excess charge with a charged conductor, is there any ampere of current?

[5614]

Hmm, I'm not 100% sure here...

 

What I do know is that in this case we have static eletricity, with electrostatics there is no flow of electrons, no current, or no normal current anyway, which is why it doesn't harm us. Yet the electrons do move within our body, that's why our hair stands on end, or at least we gain electrons which move. Maybe that is the answer, it is the gained electrons which move, not our 'normal' electrons...? Maybe!

 

So how can I answer you? Yes the electrons do move within our body, but it's not a normal current, it doesn't harm us.

[YT2095]

it`s not an analogy that requires taking appart really, but if we must, here goes (it could get overly complicated here though).

 

represent the Voltage as a riffle bullet, and the Amps as a bulldozer, and variations of that in between.

 

so we can have motorbikes like household mains, tesla coils like interceptor missiles, hyro electric generators like inter city trains etc...

 

are you SURE you want me to explain?

[Primarygun]

Current is the flow of electrons in a complete circuit.

Perhaps, " complete circuit" plays the most important role in this game.

If a metal is put onto a charged metal, is it considered as a complete circuit?

[YT2095]

nope.

 

it just becomes of the same charge.

[5614]

Primarygun: No because there is no flow of electrons, merely a transfer of electrons until an electrical equilibrium is reached ie. the charge will balance out over the two of them.

 

YT: umm, I think I'll give the analogy a skip! I'm sure it works for you, but as long as it is just an analogy and you know that the current=flow, voltage=push is the real thing as far as, well, electricity is concerned. I mean, don't take that the wrong way, some of my analogies are just, well, pretend they don't exist! But they work for me, I'm sure this one works for you, but in the nicest of ways lets keep it that way!

[Primarygun]

Someone just told me there is a current present in a nanosecond of time if I stand on an insulator and touch a charged conductor.

[5614]

I don't understand what you mean...

[Primarygun]

Anytime charges move from one place to another it is considered a current. Some currents do not last very long. If you stand on the insulator and touch a charged object there will be some current that flows into your body until you become sufficiently charged to no longer attract the charges in the object. This could happen very quickly, and it could happen with a spark that jumps between you and the charged object. The current will not persist if you are standing on the insulator unless the charge on the object is varying.

 

If you stand on an insulator and touch a conducting wire carrying household current at 115 volts ac, there will be a small current flowing into and out of your body. As long as you do not touch anything that provides another path out of your body for that charge, you probably will not even feel it. However, if there is a path through you to another object that can carry current easily, you will feel a shock as the current flows through you.

....

[YT2095]

quite correct

 

as your body will initialy start off with a charge of it`s own, and then on contact that will ballance out

[5614]

OK, but it's still travelling within you as opposed to through you, which is probably (or should I say maybe? I'm guessing) why you can't feel it.

[Spyman]

How about this analogy:

 

If You have a lake, about 100 m above sea level, (potential).

 

Will You get pushed by the water in the lake or in the sea ?

 

Now connect the two with a river, the water flows, (current).

 

Will You get pushed by the water if entering the river ?

 

The power of the push from the water or the electrical shock, (voltage * current), is what You feel.

 

So without a complete circuit there is no flow and thus no power.

 

With a complete circuit Your body becomes the river. As the human body mostly consists of water with low resistanse, then if the voltage is high enough to penetrate the natural insulanse of the skin, the shock can be considered as trying to stand in a river with the slope of the Niagara Falls.