The identification method for diodes is in the symbol of the diode circuit, where one end of the triangle is the positive pole and the other end of the short bar is the negative pole. Because diodes have a single conductivity, in a circuit, current can only flow into the diode from the positive pole and out of the diode from the negative pole. The polarity of "+" and "-" next to the diode symbol is added for ease of explanation, and is generally not added when drawing circuit diagrams When looking at a circuit diagram, beginners often have difficulty distinguishing which side of the symbol of a diode is the positive pole and which side is the negative pole. In this case, the symbol of a diode can be seen as a funnel (with a large mouth and a small bottom). Water can only enter and exit from the large mouth of the funnel, and water flow is the current. The current flows from the positive pole and negative pole of the diode, so it is natural to remember that the triangular side of the symbol is the positive pole of the diode. The shell of the diode is only marked with the model and polarity, and its main parameters are not marked like resistors, capacitors, and inductors. Based on the shell markings of the diode, the positive and negative polarity of the two pins can be distinguished. Domestic diodes usually have circuit symbols printed on the casing, directly indicating the polarity of the pins Some bipolar electrodes usually have a color ring printed on one end of the negative electrode as a negative electrode marker. The positive and negative poles of light-emitting diodes (new light-emitting diodes without pin trimming) can be identified by the length of the pins, with the long pin being positive and the short pin being negative. In addition, light-emitting diodes are mostly packaged with transparent resin, and there is a shallow plate at the bottom of the tube core to observe the size of the metal sheet inside. Usually, the pin at the large end of the metal sheet is the negative pole, and the pin at the small end of the metal sheet is the positive pole
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