# Questions tagged [rms]

Root Mean Square. Mathematical method to calculate effective value from an AC signal.

119 questions
1answer
43 views

### Tripping a circuit breaker when using a half wave rectifier

How does a half wave rectifier or phase control dimmer affect the triggering of a circuit breaker? For example, if a 20A resistive load was on a 15A breaker with a half wave rectifier. Now average RMS ...
2answers
51 views

### Confused on when to use RMS current or voltage in calculations (regarding rectifiers)

For question a, why is the power absorbed by the DC source : P=Vo*Io However, for the same exact question, the power absorbed in the resistor is P = (Irms)^2 * R Hence when do we use RMS current/...
2answers
30 views

### Is the input voltage on power adapters RMS voltage or peak AC voltage?

For example, would a laptop power adaptor with a voltage input of 100-240V ~ be safe to use in a country with 230V RMS wall voltage? Thanks in advance!
1answer
123 views

### What is the typical RMS noise of a lithium battery?

Take a typical CR2032 battery, if it is not discharging, what is the typical variation in voltage over a short period of time (eg a few seconds or minutes)?
1answer
63 views

### Random Noise Voltage

I have a signal I am interested in obtaining power from. The best way to describe the signal is that it is random. In the graph, the voltage fluctuates from negative to positive with an RMS of 0.5 ...
1answer
113 views

### PCM5102A: analog output level not what I expected?

I cannot achieve a 2.1 Vrms mentioned in their datasheet (pages 4 and 9). I can only output 1.04Vrms from the 1kHz source. Do I measure it wrong or this is what I should expect? Or maybe I get such ...
1answer
119 views

### Peak Current vs RMS Current when calculating Reactance

I am having a hard time getting a grip on AC circuit analysis. I have been taking my peak voltage/current and converting it to RMS current and RMS voltage so I can use ohms law and things like that to ...
3answers
223 views

### Calculate Angle for Triac Phase Control

Triac-based phase control of the mains power into resistive load. According to this post, https://www.physicsforums.com/threads/how-to-calculate-rms-voltage-from-triac-phase-angle.572668/#post-...
2answers
125 views

### How to Find R.M.S value [closed]

how can I find the R.M.S value of this question?
2answers
582 views

### BLDC Motor Constants: Why is my Kt and Ke different?

I'm new to working with motors. Reading up on BLDC theory, it is repeatedly said that in SI units, the Ke and Kt will be numerically equal. I downloaded the motor spec excel sheet of the T1101 motor ...
2answers
934 views

### Multimeter true RMS [closed]

I'm just getting started with electronics (arduinos and friends) and I would like to get a multimeter. As far as I can tell arduinos and any other logic chips and circuits I'm gonna be using are using ...
2answers
104 views

### AC Circuits: Determine the RMS current in the Inductor in the circuit diagram attached below. (Voltage is 40V, RMS)

Here is the image of the circuit diagram. I wanted to know the method to evaluate the RMS current in the inductor branch. I would prefer to use complex analysis!
1answer
62 views

### LTC1966 Sallen-Key post-filtering application question

Just a quick question about an application circuit in the LTC1966 datasheet. Figure 13 on page 18 shows a third order (when considering output resistance of the LTC1966) Sallen-Key filter, with a ...
1answer
163 views

### What matters, the rms or peak value of the Analog signal to choose appropriate ADC for digitization?

i have an 23 bit ADC with voltage reference of 1.4 V. If my input Analog signal is AC with frequency 50 HZ and its rms ranges from 0.2 Vrms to 1.3 Vrms. Then its peak voltages will vary from 0.28 V to ...
1answer
170 views

### how to reduce the rms value for a bridge rectifier?

hello!! can any one help me with this circuit.i need to reduce the rectified dc voltage.is it possible to reduce the R.M.S value after the bridge rectifier i.e before the capacitor? practical value (...
1answer
127 views

### Why use RMS instead of the average voltage of half the cycle for power

In a AC sine wave, the RMS voltage value is $\frac{V_{p}}{\sqrt{2}}$ where $V_{p}$ is the peak voltage whereas the average voltage value over half the cycle is $V_{p}\cdot \frac{2}{\pi}$ If we ...
1answer
52 views

### What current should be used to calculated the drop across the diode? RMS current or average current?

I was designing a power supply, following is the output bridge diode current waveform from LTSpice simulation . My intention is to calculate the power drop across the diode. What value of current (...
3answers
186 views

2answers
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### Amplifier output wattage and speaker wattage [closed]

I have a Creative Inspire M2600. The Satellite speakers have broken and I have to use another 2 speakers. A note here says the RMS Value of Satellites is 6 W each. It is bit difficult to get speakers ...
1answer
984 views

### Why RMS value used in transformer equivalent model?

The equivalent model of a real transformer is given: Why do we use RMS values of input and output voltage when analyzing the model? The main confusion comes from the fact that real transformers only ...
3answers
827 views

### What does “AC frequency response : (60-1000)Hz” mean for multimeters?

I'm considering to buy a multimeter. The following is its specs as listed at Amazon: Size:KT6666 Featuring a wealth of functions, it is intended for troubleshooting various electrical issues arising ...
3answers
531 views

### Reverse engineering a power supply characteristics

I have this schematics and the following information: connect the + of the multimeter to test point A and the ...
2answers
658 views

### Can I measure the relative output gain of a power amplifier with a multimeter?

If I wanted to measure the gain that a power amplifier provides to a signal with a multimeter, do I simply do the following: Measure the input signal's voltage e.g. 1 Vrms Turn the amplifier up to ...
1answer
1k views

### RMS of a complex waveform

For a complex waveform as follows: One can find the squared rms of the complete waveform by finding rms of individual components and then square multiplying it with the corresponding duty cycle. ...
3answers
7k views

### How to a derive average and effective values of half wave rectified sine wave and full wave rectified sine wave?

I know the basics of how to find these values from a graph, but not sure how to prove that average voltage of half-wave rectifier is peak/pi and rms is peak/2. Same for full-wave rectifier where ...
1answer
126 views

### Average power across a resistor [closed]

I am solving a problem here that asks for average power across a resistor.... the resistor is 3k and V(s) = 1.897sin(500t - 71.6)... I found 0.8 mW ....but the answer book says that it is 0.6mW ... ...
1answer
51 views

### AD736 input amplitude for 32kHZ

I want to convert a sine voltage with frequency around 32kHz , what should i keep the amplitude of this signal to get the best conversion. I looked up the datasheet , but the input range given is ...
2answers
146 views

### Output the DC average value of a waveform

I have the task of designing a circuit that will, given a sine or square wave as input, output the RMS value of that input. I believe this task essentially has three parts Squaring circuit Averaging ...
0answers
529 views

### Vrms, Vpk-pk, Vpk, Vavg for AC signal with DC offset

This might be a dumb question, but what values change when applying a DC offset to an AC signal? Does Vpk represent the maximum voltage of the signal, in which case it increases directly with the ...