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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2answers
90 views

Is it wattage that kills you and not specifically amps

First of all the actual amounts needed to kill and the body resistance is not important for this scenario. Let's say we are working with dc. Let's say that 100ma is enough to kill across the chest ...
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1answer
31 views

Battery Wattage hour requirement for 12v, 3.75 amp device? [closed]

My cpap machine resmed airsense 10 states the following numbers: DC 24v, 3.75 A As per my understanding the wattage required is 24 x 3.75 = 90 I am assuming WattHour is 90x1 = 90. If I need to use it ...
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3answers
46 views

How to lower wattage of circuit

I want to power a computer fan from a 12v motorcycle battery. Disregarding the motorcycle battery being 12.6 volts (not charging), lets say that it's a regulated constant voltage source of 12 volts. ...
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1answer
49 views

2 x 90 Ah 12v deep cycle batteries in series runs 77-90w for under 20 minutes. Why?

I am trying to understand the maths here. I have 2x90Ah 12v batteries in series (24v) and they are powering my computer. The peak power is 120w while the computer is shutting down during a power loss. ...
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1answer
68 views

Watt output of radio station

I was wondering how many watts an AM radio station outputs, and if I can calculate the watts on a tuned antenna by this equation: Where Win = the watts input for the antenna, Wout = the watts output ...
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1answer
37 views

Calculating wattage of electrical appliances

I need some help from you. I don't know how to calculate wattage of my refrigerator. It has a warmer part and cooler part. Below is its configuration. Also, if you guys don't mind, please roughly ...
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4answers
80 views

5V to 12V DC-DC converter to power an 11 watt bulb

I am trying to find a schematic to make a 5V to 12V DC-DC converter to power an 11 watt bulb. I don't know how to tell if a circuit will be able to light up the bulb. I found a schematic that might ...
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1answer
72 views

Poor-Man's Power Meter [closed]

I would like to measure the power of a very unusual ac waveform. Please say if this could work... Construct a black pvc tube with a very sensitive light to voltage converter TSL257 in one end, and a ...
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2answers
248 views

how to convert/calculate \$\text{kJ}/\text{m}^2\$ to \$\text{W}/\text{m}^2\$

I have some solar radiation data that comes in \$\text{kJ}/\text{m}^2\$. These data were formerly available for download in \$\text{W}/\text{m}^2\$. I tried to find some ways to do the conversion from ...
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1answer
74 views

Watt-hour vs Amp-hour - Battery life

This might sound silly but I am new to electronics and trying to understand the difference between watt-hour vs ampere-hour when it comes to battery life per charge. So let's consider this scenario. I ...
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2answers
68 views

Correct way to measure circuit power consumption before or after LDO

I have created a low power MCU project, and I want to measure the power consumption. I am confused with: a) the correct way to place the ammeter, before (picture A) or after (picture B) my voltage ...
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74 views

Why are AWG charts rated in amperes and not in watts? [duplicate]

American wire gauge chart is rated in Ampacity. Isn't it wise to be rated in watts? Let say a wire is rated to conduct a certain amount of current what's going to happen when the voltage goes higher ...
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1answer
79 views

How can Kill-a-watt show .1A, 12VA, but 0 watts?

I'm trying to verify whether a 10W aquarium heater is failing. It has a safety fuse that renders it permanently inoperable if it overheats by running unsubmerged, which is suspected in this case. My ...
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1answer
34 views

L6-30R with L5-20P Devices

My computer lab just got a power upgrade, now we have 208V/30A with L6-30 receptacles, in addition to what we previously had. I have some leftover rack mounted power distribution units (PDUs) given to ...
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3answers
87 views

Is a 2W resistor sufficient to dissipate 0.6W of power?

I'm looking at reducing the power of a 24V 0.1A fan by half. I've calculated that I need a 240 ohm resistor for this purpose. But I also need to choose the wattage. I'm using the following website for ...
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165 views

24V 250W motors

I am trying to make an electric go-kart. I am new to the forum, so I may be missing some information but any help is greatly appreciated. After doing some math and discussing with friends I found the ...
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10answers
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What causes a fuse to blow, the current or the power?

Fuses and circuit breakers are often specified at a certain current they will 'blow'. Increasing the current will also increase the power. So if a fuse is rated for 12V DC and 20 A, this would be ...
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0answers
38 views

Can 3 3.7 volt 6000 mah batteries power two 9 watt bulbs [duplicate]

I wanted to know if 3 3.7 volts 6000 mah hour batteries power 2 9 watt bulbs, and a 12-volt pc case fan? If so for how long?
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2answers
188 views

What would happen with a 25W bulb (g4) in a 20W socket?

I have a 20W (12V) desk lamp and a 25W (500 lm) bulb, type = G4/halogen. I know putting a 75W bulb in a 60W socket can damage it or cause it to break. In my situation there is only 5W difference. ...
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4answers
170 views

how to calculate maximum temperature of wattage on wire?

how do a calculate the maximum temperature that a certain wattage can get on a wire? I know how to convert wattage to "Celsius heat units (IT) per hour", but eventually the wire has to stop ...
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3answers
63 views

How can these two motors produce the same torque if their volt/amp ratings are different and their watts/RPM are the same

My rudimentary understanding of a DC brushed motor is speed is proportional to voltage and torque is proportional current. Therefore a 36 volt 500 watt motor should have a higher RPM rating and a ...
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2answers
151 views

Way to calculate the dangerousness level of volts+amps? (don't want to learn the hard way) [duplicate]

Is there a formula to calculate the dangerousness of amps, and volts? like watts, for example. Watts = Volts x Amps. Generally speaking, you could say wattage takes into account volts, and amps. I am ...
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3answers
171 views

12V 20A: What to do for high heat

I have 4 DC motors. they each require about 12V 9A DC (108W each), and have a potential draw of up to 12V 20A each (240W each) stall current. I am using 22 AWG insulated wire. The length of the wire, ...
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1answer
41 views

How to Calculate UPS Batteries DC to AC Efficiency?

For simplicity's sake, we will use this APC UPS for example: https://www.apc.com/shop/id/en/products/APC-Power-Saving-Back-UPS-Pro-550/P-BR550GI. It has 330W rating, loaded with 66 Watt-Hour (Volt-Amp-...
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3answers
153 views

How to estimate the temperature of a filament?

I would like to know how I can estimate/calculate the temperature of a heated filament. For example, the filament (rhenium) is 0.2mm in diameter and heated with a voltage of 6.4V and a current of 2....
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1answer
26 views

How do I pick a suitable battery for my sensor?

I'm very new to electronics, and I have a sensor which is being powered by 2 batteries in series, each 6V/3.5Ah. I believe this means the total Watt Hours is 6x3.5x2 = 42Wh. When the sensor started, ...
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0answers
55 views

How does a 5,000 watt hub motor differ from a 4,000 watt hub motor (Both BLDCs), when powered by a 72V 100Ah Lithium ion battery?

I'm trying to design a motorcycle conversion kit for an underprivileged population in a rural area. I'm currently looking at potential hub motors to be powered by my selected battery (as mentioned in ...
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1answer
84 views

Understanding relation between energy use, watts and amps

I'm looking into air conditioners and I've been unable to fully understand the relation between watts, amps and the energy ratings (in this case, the one used in the United States, the yellow Energy ...
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1answer
56 views

Real consumption of SMD5050 Led Strips

I'm building my home lights with an SMD5050 Led strips. And I'm completely lost after comparing specs consumptions with real measured data. So on, I have 5 stripes and 1-to-5 Splitter from my ...
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3answers
9k views

Max watt bulb for an old “660w 250v” table lamp? [closed]

I have an old table lamp that's imprinted "LEVITON / MADE IN USA / 660W 250V / LAMP HOLDER". I'm used to lamps with stickers that specifically tell me what max-watt bulbs I can use, usually 60W, 75W,...
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1answer
37 views

Odd problem with PSU [closed]

I don't know a much about electronics so please if you choose to help, layman terms would be appreciated. I have an old 550w PC PSU. I have used it previously with an electronic air pump to pump up ...
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1answer
62 views

Is there any device or way to measure how many watts a computer's processor is using? [closed]

I know there's a device to measure how many watts a computer is using, you get an energy meter you plug the computer into it and it tells you But I'm interested in finding out how many watts a ...
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2answers
61 views

Power consumption in watt for fluorescent lamps

I live in Egypt where the AC voltage is 220v. Yesterday i bought two fluorescent lamps (60cm and 120cm). I toke the following photos for the what is written on those lamps: Please have a look to the ...
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1answer
82 views

What determines the colour temperature of a bulb?

There are various bulb products in the market, the temperature of the bulb determines the colour of the light emitted by the bulb. For example 3000K is warm white (yellowish) 6000K is daylight (...
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12answers
6k views

Why is electricity consumption billed in watts and not amperes?

Basically the subject. Why would companies bill for wattage instead of amperes?
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1answer
171 views

What is the power consumption of a 12V adapter running 4 CPU fans?

I have a quick question here. I am not a ECE guy and just a hobbyist trying to tinker while quarantined. I have 4 CPU fans (120mm) laying around and I'm trying to re-purpose them as a small fan. ...
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1answer
57 views

Ist the radiant flux of a LED equal to the Power consumption - Power dissipated?

After I had my question How can I find the PPF of an LED? answred, I've started to look for some LEDs datasheets with the intention to find the radiant flux of then, but unfortunately all the ...
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4answers
322 views

Convert kWh to watts per m² [closed]

I am from a computer science background, I need some help with some electrical engineering problem. Electricity consumption for a home in the last 56 days is 7561 kWh. There are two floors. The ...
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1answer
132 views

How to build a 18650 battery pack without a spot welder?

I'm building an autonomous boat (which needs to get me a bottle of fine whisky from Scotland) for which I want to build a battery pack. The boat is currently powered by a cheap Li-ion battery pack, ...
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1answer
59 views

Can we get more current by reducing voltage on a power supply?

This is very basic question but I seem can't find the answer. All out there is theory, but no practical explanation about this. Assume I have a 10V 2A power supply. So in theory it outputs power of ...
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2answers
55 views

Using a US/UK voltage transformer at low end of appliance power range

I've purchased this from ebay, and the official vitaclay product spec page for the model indicates a power consumption range of 500-600W. Transformers appear to come in either 500W or 1000W, but ...
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2answers
74 views

Calculating the intensity of an electromagnetic wave

I’m a bit confused when it comes to calculating intensity versus energy of a wave. If I’m given an electronmagnetic wave with an energy of 1 eV, how do I calculate its intensity ? I know intensity is ...
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1answer
227 views

How to calculate check practically POWER of SMPS required for desktop computer

How to calculate check practically POWER of SMPS required for desktop computers I have 10 desktop pc in one PC i have a high end gaming gigabyte motherboard with AMD processor graphic card and ...
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1answer
112 views

How long can this motor run?

If I have a 48v 20Ah 1000w lithium ion battery, how long could it continually run a 48v 33Amp 2000w motor? Also, how big of a battery would I need to have it run for 45mins at least?
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1answer
45 views

Measuring the instantaneous power consumption of phone

We can get the instantaneous current consumption and battery voltage via Android's API. So if we multiply those things, can we get the instantaneous power consumption of device? (P=V.I)
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1answer
67 views

How much power is needed to run these speakers?

I have couple of loudspeakers. Each is rated for: RMS Power 60 watts Power 75 watts vc Imp 16 Ohms I am going to build an audio amp for those but not sure how much power is needed. I'm concerned ...
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1answer
31 views

Dynamic residential power system

I have a farm with solar panels. Right now, it is powering the house, and excess gets sold to the electric company. I was thinking that instead I could have the excess power bitcoin mining equipment. ...
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3answers
266 views

How do I calculate the total wattage of a dc to dc circuit?

I am trying to figure out the total wattage of the below assumed dc to dc converter circuit block diagram. Can I get it simply by just multiplying the total SUM of the system output voltages by total ...
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4answers
74 views

How to know how much energy storage has powerbank? [closed]

I just looked to this question and I don't understand how to know how much Wh this powerbank has (click "Specifications" tab), because it has different output voltages and I don't know how to ...
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1answer
114 views

Is it possible that the ampere high than the volt? [closed]

Is it possible that the ampere high than the volt? for exemple if i have 5v and 6A and how its possible that there is 30 watt and 5 volt charger?

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