Faraday Flashlight LED lights in both directions I have made a Faraday's Flashlight with 25mm ht x 25mm dia cylindrical Neodymium Magnet inside a 1 inch dia hollow cardboard pipe. Pipe is covered with 1000 turns of AWG 29 gauge wire. Ends of wire are connected to an LED. The 2 ends of pipe are sealed by a tape.
When I shake the pipe, LED lights up due to Faraday's law.
Since direction of current will reverse when magnet moves from rt end to left end Vs left end to rt end, shouldn't the LED light up only when magnet moves from 1 direction ?
Why does the LED light up on both directions ? 
Thanks
 A: The source of the voltage/current is a magnet moving through a coil of wire.  
As the magnet moves towards the coil the magnetic flux linked with the coil increases and a voltage is induce3d.
The rate of change of magnetic flux linkage will increase as the magnet gets closer and classer to the coil but will eventually the rate of change of flux linkage will start to decrease and become zero when the magnet is approximately at the centre of the coil.
At this point there will be no induced voltage.
As the magnet passes the centre the induced voltage will reverse direction and eventually become zero when the magnet is a long way away from the coil.
So the LED will be on for part of the time the magnet is passing through the coil.  

Reversing the direction of the magnet through the coil will result in a similar sequence of events and again the LED will be on for part of the time the magnet is passing though the coil.  
The key to the operation of your flash light is that the induced voltage is of the correct polarity to switch the led on for part of the time the magnet is passing through the coil.

A more sophisticate arrangement has a capacitor and a diode as part of the circuitry.
A diode between the coil and a capacitor will enable a capacitor to be charged with the correct polarity so that when an led is connected across the capacitor it emits light.
