# Tagged Questions

The unit of measurement and SI unit for power, named after James Watt. It is equivalent to energy flow per second or Joules/Second. In electrical terms $W = IR = I^2 * R = V^2/R$

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### How to replace a 50 ohm speaker with 25 ohm speaker?

I'm repairing an electronic device at home. Actually it has a non functional speaker. So I've to change it. This speaker is a 50 Ohm, 0.2 Watt. But I didn't find this one on the market, what I could ...
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### Generator requirement tool accuracy [closed]

I am building the below web application to publish for free in order to help people individuals calculate what size generator they might need in order for their specific needs. My question is whether ...
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### mAh and Wh ratings not matching with voltage of device

I was under the impression that Wh = Ah * V I have a 20000mAh battery charging device for my phone but am confused about the information provided by it on the side. It claims to have a 5V output (3....
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### Battery volts and amps for 100W LED

I am interested in building a flashlight by following this tutorial, but I only want to build a 1 LED flashlight, not 10 LEDs. It suggests using 2 batteries to supply 1000 Watts. Meaning that 1 ...
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### Input power rating on power supplies - how does max amp draw apply to 220V

If a power supply says the input power is 100-240V, ~1.5A, I'm assuming that the "1.5A" draw would be at 100V, not at 240V, right? I.e. would the total max watts be 150W regardless of the input ...
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### Arduino solar panel watt meter values reading 0's

I've been building a Arduino Watt meter for the past few weeks for a solar panel, and have successfully measured voltage and current separately. However I need to know both to calculate watts but can'...
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### Decreasing lumen and power usage

I have bought four of the very same led light bulbs two weeks ago. Their lightning characteristics appeared to be the same (brightness, angle, color). Two days ago I have realized that one of the ...
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### Inverter Generator Watt Question

I'm not sure how to search this so hopefully someone will answer. I'm rigging a floundering boat for my son and want to use LED light bars on the front and sides. I want to power then with an inverter ...
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### converting watt values over time to kWh

This is probably an elementary question, but I wanted to be sure. I have a system that reads instantaneous watts values, and stores them as "events", with a power value and a time value. According ...
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### In a solar power system, when the panel is off, does the battery determine the wattage?

I am considering putting together a solar system to power my wireless router when the power goes out. I just have one question that I cannot find the answer to: Does the wattage of the solar panel ...
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### What should be the watts of solar panel and battery size

I want to light one 70watt bulb for 12 hours at night time. I want to know what should be the Watts of the solar panel and how much Ah battery will I require? I searched many of the questions here ...
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### Does +12V to -12V = 24V?

If a battery gives me a 5V terminal and a 0V terminal I calculate power by multiplying total current of the circuit by 5V. What if the battery has a +12V and -12V terminal I'm using to power my ...
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### 450mA in CK1050 rotary switch

So i bought CK1050 rotary switch i now i realized that it's rated only for 150mA 250V AC/DC on the data sheet. I need to use it with 12V DC at 450mA so will it be safe? If you think the watts it ...
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### What permanent magnet motor is the best for the bike generator? How to decide about wattage?

I am new here.. I would like to build my bicycle generator with permanent magnet motor similar to this one Bicycle Power Basics Basically, I want to run my pedal cinema with a bike generator. I am ...
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### Can I use a power cord from a computer for an amp [closed]

I rented an amp for a keyboard but didn't take the power cord. I'm pretty sure a regular computer or computer monitor cord will fit. Is it safe? The amp says on it 175 watts. Also I have a power cord ...
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### Watts and relation with A/V

I have a doubt about some numbers I'm getting in LiveWire... Can anybody explain origin of these values? I believed that watts come from Amperes x Volts, but these ciphers are driving me crazy... I ...