Are Tiles Non-Conductors? Earth Safety in Physics Lab

[waqarrashid33]

In our Physics lab I always confuse about that durin the experiment our teacher don't avoid the touching of live connecting wires with earth(table made up of cement and have tiles on its surface).
Is tiles are non conductor?
and if there are no tiles than it will be earthed or not?

 

[schip666!]

Yup, ceramics are usually very poor conductors, along with the (dry) wood that is probably the support for the table.

The Earth Earth is a better conductor but still has a significant resistance compared to a wire.

 

[waqarrashid33]

and because of this reasistance experimentors not take this into considration during the experiments involving low voltage?

 

[schip666!]

I'm not sure what you are asking. Can you post an example of an "experiment"?

 

[waqarrashid33]

Let suppose we are prforming an experiment to verify ohm 's law.
We connect a power supply with resistor and also insert an ammeter but the wires connected with the ammeter are touching the earth.
then these wires should be eathed i.e the p.d at these points will be zero and all current will be drawned by earth.
In our experimnet these were touched with tiles and our techer says that it does not make any diffuculty.

 

[schip666!]

OK, I think I get it... There have been discussions of Earth grounding on this forum in the past which you should be able to search out and read. These might help a bit...

The general idea is that yes _everything_ is a conductor. But many things are not very good at it -- in fact there is a measure, "Conductance", that is pretty much the inverse of "Resistance". The table top has a very low conductance compared to a nice copper wire. Just as a wild guess I'd say the wire might conduct a billion times better than the table. So when you are dealing with conveniently measurable currents, a difference of 1/10^9 is way below the noise level of your equipment.

You might extend your argument to having air around your ammeter wires. Air doesn't conduct does it? Well, yes it does when the voltage is _way_ high: lightning...

If you can get an Ohmmeter to play with for a few minutes, try measuring different materials. Probably on the highest scale you won't see much of anything from your table top -- I just tried it and got nothing from my wooden desk -- but you can see that your body conducts comparatively well due to being a big sack of water and ions. A pencil lead should be somewhere in the middle...

 

[waqarrashid33]

thanks.
you made it