How to determine the conduction and cutoff of rectifier diodes?

How to determine if a rectifier diode is conducting? What is the working principle of the circuit?

After the AC input voltage is applied to the rectifier diode, how to determine whether the rectifier diode is conducting or not is the key to analyzing the correct working principle of the circuit. Remember the judgment formula: positive to positive, negative to negative, positive to negative or negative to positive.

The so-called 'positive polarity' refers to the fact that when the positive half of the AC input voltage is applied to the positive terminal of the rectifier diode, the rectifier diode conducts; 'negative polarity' refers to the fact that when the negative half of the AC input voltage is applied to the negative terminal of the rectifier diode, the rectifier diode conducts; When the positive half of the AC input voltage is applied to the negative terminal of the rectifier diode, or when the negative half of the AC input voltage is applied to the positive terminal of the rectifier diode, the rectifier diode cannot conduct.