Hi All In the below Schmtics
1.Schimatic1:
Lamp is glowing because diode is forward biased,this is correct


2.Schimatic2:
Here also lap is glowing i don't know why ,i have used 1n4007 which is having 700v AC revers blocking voltage
my applied voltage is 230v


Please any one suggest why lamp is glowing even switch(diode) open.

 

As you are using an AC supply, whichever way round you connect the diode it will be conducting for one half cycle and blocking for the other half cycle.

You would get the results you expect if you were using a DC supply.

 

The diode just Halves the voltage across the lamp.

 

As you are using an AC supply, whichever way round you connect the diode it will be conducting for one half cycle and blocking for the other half cycle.

You would get the results you expect if you were using a DC supply.

According to datashet 1n4007 should be off in reverse upto 700v Ac rite

 

According to datashet 1n4007 should be off in reverse upto 700v Ac rite

Please share any details on ac reverse voltage thing

 

The diode still conducts on one half of the cycle.

 

As stated with AC there will be forward and reverse current.
Max.

 

Hello,

You have created a half wave rectifier.
Have a look at the half wave rectifier column on page 22 of the attached PDF.

Bertus

 

As stated with AC there will be forward and reverse current.
Max.

According to datashet 1n4007 should be off in reverse upto 700v Ac rite

 

According to datashet 1n4007 should be off in reverse upto 700v Ac rite

No. Off in reverse up to 700VDC. Reversing the connections to an AC source doesn't change anything as the voltage reverses every half cycle anyway.

Read this.

 

No. Off in reverse up to 700VDC. Reversing the connections to an AC source doesn't change anything as the voltage reverses every half cycle anyway.

Read this.

Then please suggest any application related to thia

 

Then please suggest any application related to thia

Are you try to stop one Half of an AC voltage?

 

Then please suggest any application related to thia

The reference I gave in post #11 shows how a diode can produce a DC voltage from an AC input using a diode.

 

Hello,

For testing the diode , you need DC as in the following picture:

This comes from this page about diodes:
https://www.allaboutcircuits.com/te...chpt-3/introduction-to-diodes-and-rectifiers/

Bertus

 

This has nothing to do with the reverse voltage the diode can stand off. It is about the direction of current flow.

Try this:
In your simulation change the voltage source from an AC source to a DC source and you can see the diode working as you think it should. Then ask why AC operation is different from DC operation. Hint: Re-read post #14.

 

I think you're mistakenly assuming that the 230V AC source starts at ground and goes up to 230V.

Actually, your ground is the midpoint of the AC wave. That's why, as stated above, the diode is forward biased for half of every cycle. For half of every cycle, ground is a higher voltage than the source.