Generally divided into two types, capacitors and electrolytic capacitors. Capacitors have no polarity and can be connected anywhere. The shapes of capacitors are mainly flat and square. Electrolytic capacitors have polarity and cannot be connected. Otherwise, it may burst and hurt people. The polarity identification is also very simple. If it is new, the longer leg is the positive pole and the shorter leg is the negative pole. If it is an old one, there is a vertical white line printed on the surface of the electrolytic capacitor. The foot close to this white line is the negative electrode. Its shape is mostly cylindrical. When welding, you should also pay attention to the difference between the polarity and the electrode on the printed board. Some have the word "+" printed on them, so the hole close to the word "+" is The positive electrode, some are printed with a circle, and half of the circle is printed with a gold stripe. The hole on the side of the gold stripe is the negative electrode. Be careful when welding.