Relay Contact

Usually no.

If you have to ask, then the answer is no.

If you're asking for our permission to experiment, then I say go for it. You should find out a critical bit of information about relay logic. Just be careful and respect the energies you are using with this relay.

If you already understand relay logic and are asking if the compliment of a bit of information can be used in place of the original bit of information with the necessary inversion or a clever circuit design then the answer is yes, absolutely this can be done. You have to remember that relay logic is relatively slow and that these two bits are not really compliments of each other.

To the NO contact connect a relay with NC contact

Logically, no its no permitted ,but

Yeah, you can for another relay and use the NC of that, but you have to use again a third relay to confirm the on/off condition of relay no 1..

If the relay is handling DC, yes you could use a transistor to invert the logic providing the transistor can handle the current and voltage. The collector is connected to +ve side of relay contacts, and emitter to -ve side. Apply the voltage at the collector to the base of the transistor thru a resistor. When the relay is closed, the transistor is off. When the relay is open, the transistor switches on.

If the relay is handling AC, use a diode bridge circuit including the transistor, so the transistor operates on both +ve and -ve cycles. Again the base is connected to the collector as above.

There will be voltage drops associated with these circuits. If the voltage available across the relay contacts is small, you're up the proverbial.

Most relays are both normally open and normally closed. It just depends on where you attach the wires. NO and NC would refer to how that relay is used in the circuit.