is this circuit valid ?

because v = 0.6 V and 10 V can't be in parallel .

 

The voltage across the zener will not be 10V because the voltage is held at 0.6V by the diode.

 

but this is D.C not an A.C. source , do you know what i mean , the 15 volts are going to be applied at the same time to both of them , which yields two batteries with different voltage sources in parallel .

 

but this is D.C not an A.C. source , do you know what i mean , the 15 volts are going to be applied at the same time to both of them , which yields two batteries with different voltage sources in parallel .

The batteries are just a model for the diode and the zener diode which is valid under certain assumptions. Practically, you can build this circuit without blowing anything. However, the voltage across the zener will be 0.6V because the diode turns on at 0.6V and thus the zener will never turn on because the voltage will never exceed 10V. If you think it the other way you will find the same. If the zener is faster and turns on first there will be 10V across it. However, the 10V will turn on the diode and thus the voltage will drop to 0.6V again.

 

thanks , learned a new thing .