A Simple Circuit to Convert AC to DC Signal

Full-Wave Bridge Rectifiers

A popular full-wave rectifier design exists, and it is built around a four-diode bridge configuration. For obvious reasons, this design is called a full-wave bridge. (Figure below)

Full-wave bridge rectifier.

Current directions for the full-wave bridge rectifier circuit are as shown in the figure below for positive half-cycle and the figure below for negative half-cycles of the AC source waveform. Note that regardless of the polarity of the input, the current flows in the same direction through the load. That is, the negative half-cycle of source is a positive half-cycle at the load.

The current flow is through two diodes in series for both polarities. Thus, two diode drops of the source voltage are lost (0.7·2=1.4 V for Si) in the diodes. This is a disadvantage compared with a full-wave center-tap design. This disadvantage is only a problem in very low voltage power supplies.

Full-wave bridge rectifier: Current flow for positive half-cycles.

Full-wave bridge rectifier: Current flow for negative half-cycles.

For more information, you can refer to the following link:
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-3/rectifier-circuits/

In order to know more about how to use the diode, you will find a silver mark, this is the negative terminal (the n-junction). On the other hand, the other side is the positive terminal (the p-junction) as in this symbol  ( —▷|— ) to be aligned exactly as the image below:  

Test an LED:

 

An LED is a light-emitting diode. Turn the multimeter to the Diode setting. Place the positive lead on one of the pins, and the negative lead on the other. If the LED lights up, the positive lead is touching the positive pin (the anode), and the negative lead is touching the negative pin (the cathode). If it doesn't light up, the leads are touching the opposite pins.

For more information, you can refer to:
https://www.wikihow.com/Tell-Which-Way-Round-a-Diode-Should-Be