When accounting for 10% impedance tolerance, what is the appropriate multiplier to apply?

To account for a 10% impedance tolerance, you are essentially calculating the range within which the actual impedance may vary due to manufacturing discrepancies or material variations. The multiplier that represents a decrease of 10% from the nominal value is 0.9.

This is because, when you reduce a value by 10%, you multiply it by 90% (or 0.9). Therefore, if you are looking to find the lower end of the acceptable impedance range, you would multiply the nominal impedance by 0.9, yielding a value that is 10% lower.

For example, if the nominal impedance is 100 ohms, applying the 10% tolerance using the multiplier 0.9 would give you 90 ohms as the lower limit of acceptable impedance. This is an essential calculation to ensure safety and functionality in electrical systems, as it allows for variations that could impact performance.

The other choices represent different approaches to adjusting impedance but do not accurately represent a reduction of 10%. Therefore, applying a multiplier of 0.9 is the correct method for this situation.