Eddy currents and traffic lights (1 Viewer)

[Mohit7]

What are eddy currents and what do they have to do with traffic lights(signals)?

How do they work with traffic signals

 

[xiao1985]

light is initially red

car comes close

the magnet planted at the stopping line moves (due to the interaction between the eddy current and the magnet) and sends the signal to the light

light start to turn green

 

[twilight1412]

light is initially red

car comes close

the magnet planted at the stopping line moves (due to the interaction between the eddy current and the magnet) and sends the signal to the light

light start to turn green

i dont really get your explaination
i mean sure the traffic lights could be connected to a magnet at the stopping line but im also pretty sure that unless it experiences a change of flux a CONDUCTOR will not have a current induced (yes i know i cut this short) so your theory will not work unless
1. the magnet is some uber strong electromagnet whose switch in on the line (which you should not be going over anyway otherwise you'll be breaking the law)
with this theory wouldnt you think that the circuit would only be closed for an instant? meaning that the light will go green and then go back red which would mean that he is driving a read light O.O

2. magnets installed in the hoods of cars cause a change in flux in a conductor as it approachs the line causing a current to run through the conductor making the light turn green, and by doing so it will continue to experience a change of flux until the car is a certain distance away
this is completely impractical as the strength of the magnet must again be uber to cause a change of flux large enough for it to get to the other side of the traffic lights (im sure you can see the implications of this? cars attracting/repelling each other)

in conclusion i can not see how the magnet can be on the stopping line unless youd like to explain it to me in no uncertain terms XD

sorry if i sound a lil mean

 

[helper]

A fairly good explanation is found
http://www.howstuffworks.com/question234.htm

 

[xiao1985]

what i mean is there's either a permenant or electromagnet implanted on the ground... when the car moves over it, there will be a change of flux RELATIVE to the car... now, this means there will be a force experienced by the car... and also the magnet (if you don't believe, try it... get a bar magnet and weave a iron bar around) and the force experienced by the magnet will send a signal to the receptor and the receptor will go green asap...

 

[Forbidden.]

What if someone like me likes to stamp on the strip while the traffic lights are red ?
What if a motorcycle or light vehicle does not exert enough force to register a hit ?
What if a really heavy vehicle damages the mechanism with its excessive payload ?

 

[twilight1412]

What if someone like me likes to stamp on the strip while the traffic lights are red ?
What if a motorcycle or light vehicle does not exert enough force to register a hit ?
What if a really heavy vehicle damages the mechanism with its excessive payload ?

according to xiao its the iron in the car which causes both the car and magnet to experience a change in flux so if you go stamping along it then unless your loaded with iron it wont happen

 

[Forbidden.]

how much of a change in flux, is it more frequent or stronger than the change in flux of a regular DC motor or less ?

 

[twilight1412]

my guess would be that it would probably be the same as flux = BA
true it might be problematic if the magnet was extremely strong but i think that because the area of a car is just that much greater then it cancels out? i dno its just my 2 cents