# Questions tagged [calculation]

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32 views

### Calculate the ampere hour rating of a battery using current over time and voltage over time

I built a battery and measured the current and voltage of the battery over time. Is there a way I can use this information easily to calculate the ampere hour capacity of the battery?
31 views

### DC motor, confusion in specification about Current

So, I am trying to build a little robot mower, and getting all parts. So I recently buyed two DC 12V motors, here is the specs: Now I am trying to calculate how big or which battery should I use, and ...
59 views

### AC Measurement of a Transistor

I am trying to analyze a transistor circuit. I should find RMS output and input current and voltage. I have made some calculations but I am not sure of whether they are acurate or not. for input RMS ...
41 views

### Determining line-to-line vs line-to-neutral loads in split-phase panel

I have a split-phase sub-panel, with two 120V legs (red/black) and middle neutral (white). Given Hall-effect current sensor clamps around some combination of red/black/white going into the sub-panel, ...
31 views

### Heater - how to define power needed taking into account air thermal dissipation

My objective is to heat a liquid inside a bottle. I have a air gap of 2 cm between the bottle and the heating element (resistive layers). The heater and the bottle is surrounded by a bottle insulator, ...
706 views

### Can I assume that groundings in electrical circuits can be split?

Assume there's a circuit like this: What I'm asking is if I can split the grounding points like this: The reason I want to do it is just for simplicity sake. I don't have an excellent physics ...
57 views

### how to calculate C for lm7809?

I need to use a LM7809 to reduce 12-14V to 9V , the device is using 40mA at normal state when I search google for application circuit - I got all kind of valus for Cin , Cout. use this datasheet ...
58 views

### Off Grid Storage Capacitor Calculations

I'm thinking about using a very large home made capacitor as an energy storage device for a light duty off grid application, running some led lights and some 500w loads for a few hours each evening. I'...
105 views

### Air gap for a coil calculation [closed]

i would a help calculating the necessary air gap for a coil assuming an ideal magnetic material: Cross sectional area of active material = 100 mm2 number of turns= 30 Inductance= 1mH Thanks in advance
38 views

### Calculating Antenna Directivity Numerically

The equation for peak directivity of an antenna is this (example source) {D = \frac{1 }{ \displaystyle \frac{1 }{4 \pi} \int_{0}^{2\pi} \int_{0}^{\pi} |F(\theta,\phi)|^2 sin(\theta) \, d\theta d\...
48 views

### Transistor Series Regulator calculation

I am new to electronics and have a limited knowledge. I tried calculating the values for a series transistor regulator to simulate in Multisim but still could not figure out a way to do this. The two ...
61 views

### calculating voltage or current for a plain transistor (no resistor)

the short version of my question is this: how do you know what the current through a transistor will be if there are no resistors? I am reading mostly the second edition of the Art of Electronics, ...
41 views

### Calculation of the resistors values in a voltage divider

I'm working on a circuit where a 3.3v flash memory, which comunicate with SPI protocol, has to be interfaced to an 8-bit PIC microcontroller working at 5v. For the MISO signal there should not be any ...
66 views

### Calculation of switching transformer at 100kHz

I am not able to desgin transformer for switching frequency 100kHz. It´s easy to desgin usual transformer for 50 Hz. But I´m totaly out when comes to switching transformers. What material should I use?...
45 views

### Battery life estimation

I have three AA 1,5V@2950mAh Alkaline batteries in series with a discharge rate of 3% per year. My circuit has a 3V3 LDO that will work until 3V6 is reached, so each battery will need to have at least ...
252 views

### Reverse Polarity Protection Circuit with P MOSFET and Zener

I have been trying to understand the operation of the following polarity protection circuit (Diagram doesn't show the internal body diode of MOSFET): simulate this circuit – Schematic created ...
45 views

### Minimal information energy conversions [closed]

I am trying to make a generator and before making it, I would need to know how many kWh it generates, in order to make sure it is actually feasible or if I should redesign it. I am just a highschooler ...
126 views

### Cable tray width selection as per NEC 392

I would like to ask if anyone know what is the meaning of the letter b used in the formula in the table 392.22 National electrical code 2017 article 392, pic (attached)
159 views

### Capacitor Vrms vs Vpeak Rating in Transformerless Supply

Why is it that when calculating for voltage across the capacitor in transformerless power supply we need to use peak voltage not RMS voltage value. To be clear I am referring to the rating of C1 in ...
34 views

### Nodal analysis for nonlinear elements

I have this circuit. I'm trying to find the $I_{3}, U_{3}, P_{3}$. For the nonlinear element I have this volt-ampere characteristics: $I_{3} = 3U_{3}^2 -U_{3}$. That's what I am doing. Using the ...