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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Why are high power LEDs categorized by wattage, not voltage & amperage?

In searching for the correct replacement LED for a project, I've noticed that, more often than not, high power LEDs seem to be primarily categorized by their wattage. Why is this the standard? It ...
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72 views

DC motor with battery [closed]

I am new with electrical and want to install motor on my bike. I want to know how volt and watt are related in DC motor and how can they help me choose the right battery pack. If I have 1kW motor but ...
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55 views

MWh for one day expressed in MW

I have read the other question on this topic, but having gone through the answer I'm still unsure about the answer to my own, so I hope this is helpful. If a generator generated 20MWh of electricity ...
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How to measure power consumption of pulsed DC motor correctly?

I built a permanent magnet pulsed DC motor, and am trying to accurately measure power input, which proves to be harder than expected. The motor is pulsed with a 25% duty cycle square wave and powered ...
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77 views

Precisely determine the actual consumed watt of the device [closed]

What is the actual consumed watt of the device stated a value of input watt and a value of output watt which we often see it?
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67 views

Find an amplifier voltage output to match my subwoofer rating [closed]

I have two amplifiers with a subwoofer connected to each one and I was wondering how to check what the output wattage to make sure I don't blow my subs. Since they are two exact same pairs, I'll just ...
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117 views

Can I power a 100w amplifier with a 33w PSU?

I purchased a small 2 channel amplifier for a DIY audio project (Amazon link). I'm hoping I can connect it to a power supply I already have to drive a pair of small speakers. PSU: 19V 1.75A DC (33w?) ...
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22 views

When using a Primera-Line Wattage and Current Meter, is it showing AC or DC measurements?

I am new to the electrical engineering stuff and am looking for some guidance. I'm going to be designing a off-grid power system for some devices. So I will need to get the power measurements from ...
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1answer
36 views

Questions about COBs and power supplies from a beginner

I'm planning to use Citizen 1212 COBs, but I don't know how they can be used on 70 watt for each one of them, knowing that each unit will have 5 COBs. So my question is: what is the right power supply ...
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4answers
136 views

Powering a 1 watt LED using a 3 V coin cell

I was hoping to power a 1 watt LED (would be great if this is capable of powering 2 or 3 watt LEDs) with a 3 volt coin cell. Will the coin cell be able to output voltages and amperages that are ...
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71 views

Understanding the actual wattage of LED (LM301H)

LED under consideration is LM301H from samsung: Product page link - https://www.samsung.com/led/lighting/mid-power-leds/3030-leds/lm301h/ Datasheet link - https://cdn.samsung.com/led/file/resource/...
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Does different bulbs in one circuit lead to shorter lifespan? [closed]

I had a conversation with my family regarding lifespans of bulbs. They claimed that they had observed that when different wattage bulbs are plugged in the same hanging light, the bulbs would die ...
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How can it be 12VDC and 1.2A 30W?

I came across a device at home which has the specs bellow written on it: Rated Power: 30 W Rated Voltage: DC 12 V Current: 1200 mA Since P = V × I, P = 12 × 1.2 = 14.4 W Why on the specs it says 30 ...
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What do these forward currents at specified wattages mean?

An LED I'm looking at has various specs listed that I can't make heads nor tails of. It is listed as a "3W LED" supporting a 2.5V minimum and 3.6V voltage. However, "Forward voltage&...
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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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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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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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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
70 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
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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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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
74 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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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
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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
102 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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122 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
82 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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37 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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104 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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209 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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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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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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303 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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261 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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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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156 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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183 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
43 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
205 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
27 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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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
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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
93 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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13k 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
66 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
78 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
83 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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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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309 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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