Physics messing with you....

[ruggedscotty]

2nd year at secondary school, physics class...

A 24v supply.... two boxes a 24v lamp some banana plug leads and 500m of cable on a reel....


class demonstration -

hooks up a light, it lights.... so he says he want to light the other side of the school....

uses the 500m of cable connects up and the bulb lights but dim... resistance of the cable

so he gets out the two boxes, connects them up one at the 24v supply one at the bulb and the cable reel inbetween...

turned it on lamp at full brightness again. trickery indeed. and it got me interested...

Ah the joys of learning

[deeen]

The "Two Slits" experiment...

[S6PNJ]

Transformers - to do with power loss - I saw a similar experiment many MANY years ago (very early 1980s) when I was at my future secondary school for an open evening thingy, might even have been a parents evening and it was the Physics lab doing stuff to fill the gaps in-between appointments - can't remember.

Anyway - if I remember my basic physics - ramp up the voltage, lower the current - same power (P=VI) but Watts (loss) is I^2R so a lower current will result in a lower loss, hence lights stay bright as the same (or slightly reduced) power gets to the other end due to the higher voltage (or something like that...)

Edited to add - AC of course, not DC. If it's 24V DC then I give up!

Edited by S6PNJ on Monday 11th January 22:09

[Mandat]

In simple terms, raising the voltage (volts) decreases the current (amps), which in turn reduces the resistance losses over a long cable run.

This is the reason why the National Grid electricity distribution network is run at up to 400,000 volts.

[Speed1283]

If it's DC I suppose the boxes could be DC-DC converters? Raising the voltage in the first instance then reducing it in the second?

[ruggedscotty]

yup know full well now, b ut back then wow..... physicis messing with you indeed. lol