...Kindly clear my doubts.
if we pass voltage and current in reverse polarity LED and with DC source (power supply) of 2v /10mA and test the LED lead with multimeter there will be flow of voltage still but no light up . But if we test the current it be zero , is that any circuit to detect current of the LED individually ,Or this above circuit will work .
Please advise
Back to Basics:
If you apply 2.0Vdc (current-limited to 10mA) Cathode to Anode to a good LED, there will be almost zero current flow regardless of the Vf of that particular LED...
If you apply 2.0Vdc (current-limited to 10mA) Anode to Cathode to a good LED, there might be almost zero current flow if the Vf of that particular LED is 2V or greater. There might be significant current flow if the Vf of that particular LED is less than 2V.
This means that 2V is not a good test voltage for determining which way a LED is connected. current flow...
Here is a better method:
There are four possibilities as shown above.
Note that the 4.5V was carefully chosen to be greater than the Vf of any LED I have seen, but less than 5V, which is the "never-exceed" allowed reverse voltage that can be applied to most LEDs without damaging them (at least, not without limiting the current to a few tens of uA).
Unfortunately, by looking at the voltage at B or C, you cannot tell if the LED is installed reverse or is missing.
If you need to distinguish between those two cases, I have a more complicated circuit that would do that.