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 answer the question about what AC meters measure in alternating current circuits, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding AC Supply**:
- In alternating current (AC) circuits, the voltage and current vary sinusoidally over time. This can be represented mathematically as:
- Voltage: \( V(t) = V_0 \sin(\omega t) \)
- Current: \( I(t) = I_0 \sin(\omega t + \phi) \)
- Here, \( V_0 \) and \( I_0 \) are the peak values (maximum values) of voltage and current, respectively.

2. **Definition of RMS Value**:
- The Root Mean Square (RMS) value is a statistical measure used to calculate the effective value of an AC signal. It is particularly useful because it allows us to compare AC values to equivalent DC values.
- The RMS value for voltage is given by:
\[ V_{RMS} = \frac{V_0}{\sqrt{2}} \]
- Similarly, the RMS value for current is:
\[ I_{RMS} = \frac{I_0}{\sqrt{2}} \]

3. **Function of AC Meters**:
- AC meters are designed to measure these RMS values rather than the peak values. This is because the RMS value provides a more accurate representation of the power delivered by the AC circuit.
- Therefore, when we use AC meters in a circuit, they measure:
- The RMS voltage (\( V_{RMS} \))
- The RMS current (\( I_{RMS} \))

4. **Conclusion**:
- In summary, AC meters measure the RMS values of voltage and current in alternating current circuits, which are essential for understanding the effective power in the circuit.