In alternating current circuits, the a.c. meters measure

Options

A. r.m.s. value
B. Peak vaue
C. Mean value
D. Mean square value

Answer

To solve the question regarding what AC meters measure in alternating current circuits, we can follow these steps:

### Step 1: Understand the AC Voltage Waveform
In an alternating current (AC) circuit, the voltage varies sinusoidally with time. The voltage can be represented mathematically as:
\[ V(t) = V_0 \sin(\omega t) \]
where:
- \( V(t) \) is the instantaneous voltage,
- \( V_0 \) is the peak (maximum) voltage,
- \( \omega \) is the angular frequency,
- \( t \) is time.

### Step 2: Define Peak Value
The peak value \( V_0 \) is the maximum voltage reached by the AC waveform. It is important to note that this value is not what is typically used for calculations in AC circuits.

### Step 3: Define Root Mean Square (RMS) Value
The root mean square (RMS) value of an AC voltage is a measure of the effective voltage. It is defined as:
\[ V_{rms} = \frac{V_0}{\sqrt{2}} \]
This value is significant because it gives the equivalent DC (direct current) value that would produce the same power in a resistive load.

### Step 4: Conclusion
AC meters, such as voltmeters and ammeters, are designed to measure the RMS value of the alternating current or voltage. Therefore, the correct answer to the question is that AC meters measure the root mean square value.

### Final Answer
In alternating current circuits, AC meters measure the root mean square (RMS) value.

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