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Questions tagged [watts]

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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heat dissipation in watts of equipment in a box

Here is the situation, some electrical equipment will be in low ambient temperatures and I need to make it warmer so that there is no damage to it. I want to calculate how much power in watts is ...
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When charging rechargable battery, should we care about watts and ignore voltage and current?

I know this might be a silly question, but it's from a beginner. Let's say I want to charge a rechargable lithium-ion battery, so when I charge it should I only check the watts and ignore voltage and ...
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65 views

How can a 12V 80Ah Battery be 1800W? Shouldn't it be 960W?

How can a 12V 80Ah Battery be 1800W? Shouldn't it be 960W? I was looking for 12V 80Ah Deep Cycle Batteries on Amazon and most of them were 1800W. Like this one: https://www.amazon.com/Cycle-Battery-...
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Transistor Inverter - when does excessive small wattage become a problem?

I'm trying to choose the best values of resistors given the stock I have so that I can deliver sufficient power and current to an HM-TRP radio module. In this circuit, I used the 100K resistor ...
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1answer
71 views

What defines Volts, Amps, Watts and mAh?

My current understanding is as follows: Volts: Speed of electron flowing. Amps : Number of electrons flowing. Watts: Amps x Volts measured for "some" time. mAh: Very confused to come up with ...
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1answer
72 views

How does a Hall-based wattmeter work?

I read about the Hall effect and understand its usage in sensors like speedometers, but I also read it can be used as a wattmeter. How can it happen? In order to calculate power (P) we need to ...
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2answers
60 views

Soldering station: power confusion

i wanted to ask what the different power/watt indictors for a soldering station actually mean in terms of the performance of the station or whether the number is just some marketing term. Some ...
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5answers
111 views

A basic question about amps, watts, and charging batteries

Why do we speak of watts (and not amps) when we refer, for example, to the "7.5W Wireless Charger for iPhones," but when we talk about cord-based USB charging, the specs typically refer to amps (and ...
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32 views

Lower wattage of IR bulbs permanently

I have two 90w/12v infrared IR bulbs which is put into a r7s sockets. From thes socket goes in total four wires which is connected to our power supply. We have set two of the wires in serial so they ...
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2answers
77 views

Why does curling a wire decrease its amperage/wattage? [duplicate]

I picked up an extension cord today, and I noticed that it had a different value for its wattage and its ampage, based on whether the cord is wound around its base or not. (I apologize that the ...
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1answer
57 views

how do LED controllers work

I’m trying to find out if a device only draws the watts it needs to run or if it takes all available For example I have led light that’s says max 0,75 watts and the led controller says output 144 ...
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65 views

Electrical Power Question

I am trying to compare watts exiting the battery vs watts being consumed by the bulb. I have set up a test circuit shown below. Should not A-B watts match C-D watts?? Sorry for such a basic ...
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1answer
59 views

Are watts consumed in wireless electricity? [closed]

If I put a transistor on a coil of wire connected to a 120v AC circuit, and made it so my toaster was now wirelessly powered, if I turned the toaster on would it consume watts that are able to be ...
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2answers
141 views

Why does my phone charger consume more electricity (watts) when delivering less amps (slower charging)? [closed]

As far as I could understand, the charging speed is measured in amps. Like, if I use Ampere, it will tell that it charges in 2.5 amps, or 1.5 amps. I hope I got this right. Amps is the only ...
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2answers
87 views

How can I measure an induction cooker’s power with an oscilloscope?

I have to measure the current and voltage of a coil with an oscilloscope. In this case, does P Watt = Irms*Vrms? The induction cooker writes that the maximum Watts is 1.2K, but I measure it over 1.2 ...
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1answer
33 views

Is it okay to run a Mercury Vapor Lamp of lower wattage (100/150/175W) on a 400W MHL/MVL ballast? Also can a 60Hz ballast be used in 50Hz?

So, I have this RAB BMHH400PSQ Metal Halide Pulse Start Ballast 400W ,M135/M155 MULTI TAP 120-277V with me. Since the MVL are being phased out it has become quite difficult to get a ballast for one of ...
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2answers
237 views

Alternatives to High Wattage Resistors? (Do multiple low-wattage resistors equal a single higher wattage resistor?)

I am a beginner, so I may have made a horrible mistake in my diagram, but I am trying to learn. According as I have figured it, I am having an issue wherein I need a resistor rated for a minimum of ...
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1answer
55 views

How can I interpret the readings of a USB voltage tester considering the input voltage is 5V and I am charging a 3.7V battery?

I have this USB voltage tester that I place between my usb wall charger and a USB charging cable. This device gives me the total current that went through over a period of time. Let's say after 2.5h ...
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1answer
2k views

Motor current consumption and power do not match

I am working on a design and need to calculate the energy consumption of this motor: https://www.maxonmotor.com/medias/sys_master/root/8825428410398/17-EN-256.pdf. (Part No. 339252) The ...
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1answer
97 views

How to properly read Watt of a bulb power?

I'm confused about reading the terms Watt, Wh, and Ws of bulbs. Here is the quoted text taken from an electrical book that I'm currently reading on : Now I'm take out some points from the remarks ...
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1answer
59 views

A question about my refrigerator [closed]

it's written on my refrigerator 500watts.. I want to know how much it consume watts per month. let's consider that the compressor of the refrigerator works 10 hrs per day.
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1answer
385 views

12 Volt vs a 24 Volt Motor

I have read that using a higher voltage motor would need less current to get the same power. I understand that P = IV and how that works. My question is if the 24 V motor would get half of the current,...
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1answer
37 views

why does a potencial coil in wattmetter influences the pointer rotation

can somebody tell me, why does a potential coil in wattmetter influences the pointer rotation. if the ideal potential coil doesn't have current, it would not generate a magnetic field and it would not ...
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2answers
395 views

12 v watt heater with nichrome coil [closed]

i am new here. First of all I am sorry for my bad english. I want a help from those who know about nichrome heater coil. I want to make a 12v dc incubator using nichrome wire as heating element, all ...
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1answer
21 views

What wattage should I use for a switching adapter?

I have a bad switching adapter. It has a DC output of 14.5V 2.48A Max. I can't find a match anywhere. I think a 3.0 Max will work, but I don't know the wattage. The replacements I've found are 29W, ...
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1answer
77 views

Step up voltage Transformer for more watt?

Using generator in mountain or underground tunnel location, construction workers from portable generator gets maximum: AC Output: 220volt as 200 to 250watt Now, they need to use a machine for ...
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1answer
86 views

Does a 5w LED lamp require 5w/per hour to run ?

Does a 5w LED lamp require 5w/per hour to run ? eg. would 200 x 5w LED lamps running for 1 hour would require 1kwhr of electricity. Or is the 5w related to some other time scale ?
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1answer
885 views

How many watts does tweeter needs

I have a speaker with the following specs: Max. power - 600W Impedance - 4~8 Ohm Freq. response - 45Hz-20KHz Sensitivity - 98dB/W/M The tweeter of the right speaker is not working so i want to ...
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0answers
149 views

How can I measure the power given to a USB WiFi adapter's antenna in dBm or mW?

I have an Alfa AWUS036ACH USB WiFi adapter, and would like to know how much power is being given to the antennas (in dBm or mW). The Amazon link to it is here: https://www.amazon.com/Long-Range-Dual-...
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1answer
91 views

Not sure if this capacitor will blow up [closed]

so i have just bought a fan controller(silverstone cpf04) and it is rated with 2200μF and i am planning to connect 7 fans to it. (NF-F12)4 fans are each rated with 12v operating voltage 3.6w input ...
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1answer
51 views

Figuring out wattage

I know I can take volts * amps to figure out watts, but what if the device accepts a range of volts? So if I have a device that takes 100-240 volts, and is 2 amps, what is the wattage being used? Does ...
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711 views

How many D batteries would be required to power an 150watt/120volt Light for 8 Hours?

Here are the links to further data. Bulb info. D battery datasheet.
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3answers
846 views

How convert kWh to W

I want to know if there is an approximate or exact way to know the consumption in watts of household appliances in a house from the monthly consumption that reaches the bill. Taking into account that ...
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2answers
47 views

How to calculate battery ratings for your solar panel?

If I want to choose a battery for my solar panel which is required to run a load of 5 kWh/day. Then I will be needing a battery with a rating of above 23 ampere hours since 5 kWh/220 V (since 220 V we ...
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1answer
198 views

10 W LED COB on 12 V

So say I have a 10 W LED, most have a forward voltage of 9-11 V and a maximum current of 700 mA. If I wanted to connect it up to 13 V (a fully charged SLA battery) couldn't I simply do 11-13=2 (LED ...
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1answer
84 views

Converting 110v at 8.5 amps to 208 three phase amperage [closed]

I have some equipment that uses 8.5 amps and 1050 watts on a 110v. Any idea what the amperage would be on 208 three phase?
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1answer
57 views

Wattage of DC device is not equal to AC [closed]

I have a led driver (LPC-20-700) that is 30V and 700mA, which makes it 21W. I run 10 leds (≈ 2.8V drop) in series with it and it is an constant current device. If I plug my multimeter between, I do ...
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1answer
94 views

How is output power related to input power? [closed]

Please Note: I stumbled upon this forum after considerable googling but was not able to understand the answers I found. Your simplest terms and explanations are appreciated. I plan to bring a piece ...
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1answer
435 views

Power supply for Audio amplifier : high-voltage based watts or high-current based watts? [closed]

So I have these Philips (FW-V355) speakers, and I want to connect them to my PC via AUX or Bluetooth, ofc I separated them from their original old system/amplifier. In order to realise that, I bought ...
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1answer
253 views

Help with calculating voltage using watts/ohms (batteries/coils)

Okay, so I have no experience in EE (I do SE), so I don't know where to start. I apologize in advance this isn't the right place for this kind of question. I bought a vaporizer with a small battery a ...
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0answers
34 views

Replace a power adapter 12V/1A DC with 15V/0.8A [duplicate]

I have a battery-charger that has an input of 12V/1A as specified in the specs. Can I replace the adapter with a 15V/0.8A ...
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2answers
157 views

How do you measure/detect Watt-Seconds? [closed]

As part of a project I am working on, I am required to measure watt-seconds. I've looked this unit up online and it typically references to a camera flash. My question is how does one measure/detect ...
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2answers
71 views

Power calculation in kwh over a period of time with a variable current source

I have an experiment running which generates variable current due to a chemical reaction over a period of 8 hours. I sampled the current at each hour with a constant voltage supply of 12V. When i use ...
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7answers
2k views

Calculate the electric bill of a phone charger (AC adapter input or output?)

I need to calculate the amount of money I pay for charging my phone with this charger I know that I need to calculate the watts then kWh, so I multiplied 5 V by 1.55 A to get 7.75 watts and then use ...
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1answer
48 views

Plotting the instantaneous power of an RLC circuit

So I've been solving some basic instantaneous power/ average power problems and I've been asked to "draw" $$p(t)$$ which is the instantaneous power function of the circuit, I guess there are two ways ...
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3answers
105 views

Power plant cost accounting

For a 300 MW power plant, 14.5 MJ / kWh of heating capacity must be provided. For this you can use coal with a heating value (hW) of 29 MJ / kg and a price (P) of 35 € / t or gas with a calorific ...
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1answer
156 views

How can this MOSFET become overheated? How big should the heatsink be?

I've got a very simple circuit. A MOSFET (TK15D60U) is powering a 3 to 4 Ohm heat bed by 19.6 volts. From my calculations this results in 6.5Amps. The power adapter seams to have its specs at max 6....
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1answer
185 views

Will a man get electrocuted if he places the electrical test screwdriver on his foot?

Below is the typical circuit when somebody do the "test light" on wall electricity socket (Image 1): In this "images 1", very little current will flow into his body, because the high electrical ...
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2answers
57 views

Can I use low voltage but higher maximum amperage?

I have an electronic device (electromagnet solenoid) that working on 9V/DC and 30mA current (9*30=270mW) Question 1: If there is a 5V/DC adapter that could produce maximum 54mA (5*54=270mW), could I ...
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1answer
42 views

If watts exceeds rating? [duplicate]

I have been reading quite a lot on the subject in the past hour and I don't seem to be getting an answer, just about amps. I have a 2 watt rated ball valve, and I have a 12v dc 1 amp power supply. W = ...