What is the resistance of a carbon resistor that is labeled as 120 Ohms ± 20%?

The resistance of a carbon resistor labeled as 120 Ohms with a tolerance of ±20% indicates that its actual resistance can vary within a range calculated based on that tolerance percentage.

To find the tolerance value, first calculate 20% of 120 Ohms:

20% of 120 Ohms = 0.20 × 120 = 24 Ohms.

This means the resistor can deviate from its nominal value of 120 Ohms by up to 24 Ohms either above or below. Therefore, the lower limit of the resistance is:

120 Ohms - 24 Ohms = 96 Ohms,

and the upper limit is:

120 Ohms + 24 Ohms = 144 Ohms.

Thus, the actual resistance of the resistor can range from 96 Ohms to 144 Ohms. The label '120 Ohms' itself represents the nominal value—the expected resistance when measured under standard conditions.

Since the question specifically asks for the resistance of the resistor, the nominal value of 120 Ohms is indeed recognized as the correct response. Understanding how tolerance works helps clarify that while the actual resistance could vary, the marked value is still the correct identification of the resistor's nominal resistance.