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Examples: Resistor Specifications

<^< Resistor Specifications | Course Index | Preferred Values: Resistors >^>(:nl:)

>>frame round<< Example 1:

A resistor has a marked value of 470&#937;.

Determine the tolerance of the resistor if it has a measured value of 455&#937; >><<

>>id=example1 class=question margin=10px frame round<< The difference between the marked and measured values of resistance (the error) is (470&#937; - 455&#937;) = 15&#937;. The tolerance is given by:

Tolerance = error / marked value x 100%

The tolerance is thus 15/470 x 100 = 3.2% >><<

>>frame round<< Example 2:

A 12V power supply is to be tested with a 12&#937; load resistor.

If the resistor has a tolerance of 10% determine:

(a) the nominal current taken from the supply (b) the maximum and minimum values of supply current at either end of the tolerance range for the resistor. >><<

>>id=example2 class=question margin=10px frame round<< (a)If a resistor of exactly 12&#937; is used the current will be:

I = V/R = 12V/12&#937; = 1A

(b) The lowest value of resistance would be (12&#937; - 1.2&#937;) = 10.8&#937;. In which case the current would be:

I = V/R = 12V/10.8&#937; = 1.11A

At the other extreme, the highest value of resistance would be: (12&#937; + 1.2&#937;) = 13.2&#937;

In this case the current would be: I = V/R = 12V/13.2&#937; = 0.91A >><<(:nl:)(:table style="clear:both":)