Understanding Ammeter Accuracy and Limiting Error

An ammeter is a device used to measure electric current. Like all measuring instruments, ammeters have limitations in their precision, defined by their accuracy rating. The limiting error represents the maximum possible deviation between the measured value and the true value, as specified by the manufacturer. This is often expressed as a percentage of the instrument's full-scale reading (FSR).

Calculating the Ammeter's Limiting Error

To find the limiting error for the given ammeter, we need to follow these steps:

1. Identify the Given Parameters:
   • Ammeter Range (Full-Scale Reading, FSR): 25 A
   • Guaranteed Accuracy: 1% of Full-Scale Reading
   • Measured Current Value: 5 A
2. Calculate the Absolute Limiting Error:

   The accuracy is given as 1% of the full-scale reading (25 A). The absolute limiting error is the maximum error the instrument can exhibit under specified conditions. We calculate this as follows:

   Absolute Limiting Error = Accuracy Percentage × Full-Scale Reading

   Using LaTeX for the calculation:

   $$ \text{Absolute Limiting Error} = \frac{1}{100} \times 25 \, \text{A} $$

   $$ \text{Absolute Limiting Error} = 0.01 \times 25 \, \text{A} = 0.25 \, \text{A} $$

   This means the actual current can be anywhere between $5 \, \text{A} - 0.25 \, \text{A}$ and $5 \, \text{A} + 0.25 \, \text{A}$, based on the instrument's specification.

3. Determine the Error Value Presented in Options:

   The options provided are 0.05, 0.04, 0.025, and 0.02. Our calculated absolute limiting error is 0.25 A. Let's see how this relates to the measured value and the options.

   The question asks for "The limiting error". While the absolute error is 0.25 A, the options seem to represent this error in a different context, possibly relative to the measured reading. Let's calculate the ratio of the absolute limiting error to the measured current:

   Ratio =  (Absolute Limiting Error) /  (Measured Current) )

   Using LaTeX:

   $$ \text{Ratio} = \frac{0.25 \, \text{A}}{5 \, \text{A}} $$

   $$ \text{Ratio} = 0.05 $$

   This calculated ratio, 0.05, matches one of the options provided.

4. Conclusion:

   Based on the calculation relating the absolute limiting error (derived from the full-scale reading accuracy) to the measured current value, the limiting error is represented as 0.05 among the given options.