How to judge the positive and negative poles of electrolytic capacitor?

Electrolytic capacitor is a kind of capacitor. The medium has electrolyte coating and polarity. The positive and negative poles cannot be connected incorrectly. The capacitor is composed of two metal poles sandwiched with insulating material (medium). There are two main types: aluminum electrolytic capacitor and tantalum electrolytic capacitor. Do you know how to judge the positive and negative poles of electrolytic capacitor? How are its positive and negative poles connected?

Positive and negative electrode judgment of electrolytic capacitor

Bolt type electrolytic capacitor. Generally, the "+" (positive pole) and "-" (negative pole) are written very clearly on the outer surface, just beside the two terminals

Solder aluminum electrolytic capacitor. The surface is also marked with negative pole or "-" symbol. Generally, the negative embossed weld leg is also used as the mark at the bottom of the weld leg

Electrolytic capacitor can also be judged by the different lengths of two pins. The long pin is the positive pole, and the short pin is the negative pole

Connection of positive and negative electrodes of electrolytic capacitor

Electrolytic capacitor is a kind of capacitor. The metal foil is the positive electrode (aluminum or tantalum), and the oxide film (aluminum oxide or tantalum pentoxide) close to the positive electrode is the dielectric. The cathode is composed of conductive materials, electrolyte (electrolyte can be liquid or solid), and other materials. Because the electrolyte is the main part of the cathode, electrolytic capacitor is named. At the same time, the positive and negative of the electrolytic capacitor cannot be wrongly connected.

The reason why the aluminum electrolytic capacitor has polarity is that the aluminum oxide film on the positive plate has a single conductivity. Only when the positive pole of the capacitor is connected to the positive pole of the power supply and the negative pole is connected to the negative pole of the power supply, can the aluminum oxide film act as an insulating medium. If the polarity of the aluminum electrolytic capacitor is reversed, the aluminum oxide film will become a conductor, and the electrolytic capacitor will not only fail to function, but also damage the capacitor due to excessive current passing through it.

What is the effect of the polarity reversal of the electrolytic capacitor?

Because of the positive and negative polarity of the electrolytic capacitor, the positive and negative poles cannot be reversed when used in the circuit, and generally cannot be used in the AC power circuit. When used as a filter capacitor in the DC power circuit, the positive pole of the electrolytic capacitor is connected to the power output terminal and the negative pole is grounded when the positive voltage is output, and the negative pole is connected to the output terminal and the positive pole is grounded when the negative voltage is output.

When the polarity of the filter capacitor in the power supply circuit is reversed, the filtering effect of the capacitor is greatly reduced.

On the one hand, the output voltage of the power supply fluctuates, and on the other hand, the electrolytic capacitor equivalent to a resistor at this time heats up due to reverse energization. When the reverse voltage exceeds a certain value, the reverse leakage resistance of the capacitor will become very small. In this way, the capacitor will be damaged due to overheating after being powered on for a short time