What is indicated by the fourth band in a resistor's color code?

The fourth band in a resistor's color code is designated to indicate the tolerance of the resistor. Tolerance is a crucial specification as it defines how much the actual resistance can vary from its stated value. For instance, a resistor with a 5% tolerance can have a true resistance that is 5% above or below the nominal value. This measure helps users understand the reliability of the resistor's performance in a circuit.

Other options do not align with the purpose of the fourth band. The number of zeros or the specific material used in the construction of the resistor are typically represented by other bands or characteristics. The maximum current that a resistor can handle is also not indicated by the color bands; it is usually specified separately in the product data sheet or by the resistor’s physical design rather than being encoded in the color code itself.