Subelement A: Principles— Topic 6: Electrical Measurements
Question 3-6A1
Element 3 (GROL)An AC ammeter indicates:
Explanation
An AC ammeter indicates the **Effective (RMS) values of current**.
Here's why:
Alternating current (AC) constantly changes direction and magnitude. The Root Mean Square (RMS) value is the standard way to quantify AC because it represents the "effective" current. This means that an RMS current will produce the same heating effect in a resistive load as a DC current of the same magnitude. For a pure sine wave, the RMS value is approximately 0.707 times the peak value.
* **A) Effective (TRM) values of current:** "TRM" is not a standard electrical term. While meters can be "True RMS" (accurate for non-sinusoidal waveforms), "effective" is a description of RMS, not a separate unit.
* **C) Peak values of current:** Peak current is the maximum instantaneous value. While important for voltage breakdown or transient analysis, it doesn't represent the continuous power delivery that an ammeter typically measures.
* **D) Average values of current:** For a symmetrical AC waveform, the average current over a full cycle is zero, as the positive and negative halves cancel out. This wouldn't be useful for measurement.
Related Questions
3-69K5 The amplitude modulated variable phase signal and the frequency modulated reference phase signal of a Very-high-frequency Omnidirectional Range (VOR) station used for aircraft navigation are synchronized so that both signals are in phase with each other at ____________ of the VOR station.3-69K6 What is the main underlying operating principle of the Very-high-frequency Omnidirectional Range (VOR) aircraft navigational system?3-6A2 By what factor must the voltage of an AC circuit, as indicated on the scale of an AC voltmeter, be multiplied to obtain the peak voltage value?3-6A3 What is the RMS voltage at a common household electrical power outlet?3-6A4 What is the easiest voltage amplitude to measure by viewing a pure sine wave signal on an oscilloscope?