How can you tell if a capacitor is positive or negative?

In most electrolytic capacitors, which are common types of capacitors, you can distinguish between the positive and negative terminals by looking at the capacitor's physical characteristics and markings. Here's how to tell the positive and negative terminals apart:

Markings: Electrolytic capacitors typically have markings on their body that indicate the polarity. You may see a stripe with a series of negative (-) symbols running down one side of the capacitor. This side with the stripe is the negative (-) terminal.

Longer Lead: In through-hole electrolytic capacitors (those with wire leads), one of the leads is typically longer than the other. The longer lead is usually the positive (+) terminal, while the shorter lead is the negative (-) terminal.

Axial vs. Radial: In some electrolytic capacitors, especially axial types, the negative terminal may be marked with a colored band near the negative lead. The positive lead is usually longer in axial capacitors.

Casing Shape: In aluminum electrolytic capacitors, the shape of the casing can also help you identify the polarity. The negative (-) terminal often has a flat or slightly concave surface, while the positive (+) terminal is more pointed or rounded.

Silk Screening: On surface mount electrolytic capacitors, you may find markings like a '+' sign near the positive terminal and a '-' sign near the negative terminal.

Datasheet: If you have access to the datasheet for the specific capacitor, it will always provide information on the polarity, including which terminal is positive and which is negative.

It's crucial to observe the polarity of electrolytic capacitors because connecting them incorrectly can lead to capacitor failure, overheating, or even damage to the circuit. Non-polar capacitors, such as ceramic capacitors, don't have a specific polarity and can be connected in either direction. Always double-check the markings and datasheet to ensure proper connection, especially when dealing with electrolytic capacitors.