Watt Definition and 78 Threads

The watt (symbol: W) is a unit of power or radiant flux. In the International System of Units (SI), it is defined as a derived unit of (in SI base units) 1 kg⋅m2⋅s−3 or, equivalently, 1 joule per second. It is used to quantify the rate of energy transfer. The watt is named after James Watt (1736-1819), an 18th-century Scottish inventor.

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  1. T

    Why Does a Light Bulb's Resistor Burn Out When Directly Connected to an Outlet?

    I was with my electrician friend the other day, and we stuck two copper wires into each of the holes of a regular 120V outlet then smashed a 100W light bulb and took the resistor (small coiled looking thing) out of it and set it on a piece of wood and touched the copper wires to each end of the...
  2. phy_optics

    Converting Lux to Watts: A Quick Guide

    Hello frnds! Can anybody convert the following factors? V/(lx-s) to V/(um/cm2) at 555nm ?? Thank you.
  3. D

    Finding Power in watt with a real battery

    Homework Statement calculate the power dissipated by a resistor R connected to the battery when R = 2.4 ohm. Homework Equations I=V/R The Attempt at a Solution I found A of battery that given and put R value given to find P, however I cannot get a right answer. What did I...
  4. S

    How to Calculate Watt: Understanding the Basics

    ive always been interested in calculations, so i want to try to calculate watt but I am stuck bear in mind this is a pure hobby for me and i am far from a math genious in this example i use a car here is how far i have come it accelerates from 22.2m/s to 33.3 m/s in 7 seconds to...
  5. U

    Watt needed to heat up an iron, correct?

    an IRON cube with (Length 1.3cm Width 1.3cm Height 0.7cm) so Volume = 1.183cm^3 density of an IRON = 7.8gm/cm^3 so Mass = 9.2274gram Q=mcT c for iron = 0.450 J/(g·K), T difference = 160 degree celsius Q=9.2 . 0.45 . 160 Q=662.4Joule 1Joule = 1 Watt.second so if i need to heat...
  6. C

    Power (Watt) of Magnetron and Klystron

    If a microwave generator (for e.g., magnetron or klystron used to particle accelerator) is said to have power of for e.g. 3 MW, what does that depend on? Is it related to the electric field amplitude of the electromagnetic wave and how many waves are coming out of the microwave generator and...
  7. neduet

    Transformer and watt or VA relation?

    Hi friends it is not ( problem or numerical) just i want know friends if i have 15kva transformer . then can i say it can carry 1500 watt 10 (split AIR conditioners) as a load. and what happened if i add 5 more (split AIR conditioners) in same case. just give me idea...
  8. K

    How is the 90-degree phase shift achieved in a Var transducer?

    A Watt transducer has line to line voltages and line currents as inputs. It calculates the Watts and outputs DC mA. The one i am working on is rated 1mA DC for 500W AC. The relationship is linear. A Var transducer does exactly the same, but it shifts the input AC by 90degrees to get Vars...
  9. D

    Can a 10 Watt Globe be Powered by 24V?

    Is it possible to light a globe - a normal energy efficient globe of 10 Watt usually powered by 240v or so. Can the globe be powered if I use 24v and put a lot of amps to power it up? According to the PIE formula (Watt/Current*Volt) thanks
  10. M

    5 watt radial turbine design - I need conceptual help

    I'm looking to design a radial turbine to deliver 5 watts from compressed air (60-90psi) at 20,000 to 40,000 RPM. 30% efficiency would be suitable. I reviewed related patents-got little from them. I also reviewed my college textbooks, but they address incompressible, momentum transfer...
  11. L

    Need help with a 12 watt Audio amplifier

    I have recently built a 12 watt amplifier spec'd by G. Randy Sloan. The problem I am having is many fold. 1.) I am not an EE and learning as I am going 2.) The amp WILL carry a signal but so far I have only been able to use it as a passive circuit. 3.)The output leads don't provide an...
  12. A

    How Many Watts Are Needed to Lift a 200-Pound Mass with an Electromagnet?

    How do I figure out how many watts per hour or horse power it takes to lift a 200 pound mass using electro magnet? Is there a formula I can use? Thanks for any help
  13. C

    Car Battery and 120vac 100 watt bulb

    Can a 12 volt car battery illuminate a 120vac 100 watt bulb ? I not sure if a bulb that is rated for 120 volts can still be powered with a battery pushing 12 volts. I think the 100 watt bulb only needs 1 amp to be illuminated with the 120 volts. I'm still trying to figure out the basics...
  14. M

    Calculating Watt/Watt-Hour for 20W Light Bulb & 8W Wind Turbine

    1. A light bulb which is 20Watt, is run for 2 hours equals to 40Wh, which mean 40Watt used in an hour is the concept correct? 2.Assume above was correct. The 20Watt is powered by a battery which is 200Watt. This battery can last for 5 hours. IS the concept above correct? 3. A wind turbine...
  15. E

    How Do I Calculate the Power Output of a 38 Watt Amp?

    I have a 38 watt amp and I'm trying to figure the Power it produces, but I'm not sure how to find the Velocity. Can anyone clue me in on this? And I know to use the P=V^2/R And sorry if this is in the wrong forum, I'm new. Thanks EDIT: I just found V=f/Lw (velocity=frequency/wavelength) but...
  16. L

    Which Adapter Requires More Watts for My Device?

    If I have 2 electrical adapters for a specific device, which has the following information on them: 1- 230va/50hz/20mA 4vdc/150mA 2- 230vac/50-60hz/65mA 6.5vdc/600mA ps66/2061 IP40 IEC60950 T45/E How can I know, how many watts each of them require? I know that the watt = Volt x...
  17. G

    4500 Watt inverter to power a laptop

    I hope somebody can help me understand what is going wrong. I have a Gateway laptop with an ac power supply rated for up to 4.7 amps. I have an inverter rated for 4500 watts and 4.2 amps that I bought from Sam’s Club. It was made by Black and Decker. When I plug my laptop into the inverter I pop...
  18. P

    How Does Wattage Affect Rowing Performance and Energy Costs?

    I had question in practice book, i answered all the math problem, but i couldn't figure out the explantation part of the question a) describe the relationship between the time to complete 2000 meter and the average wattage output in rowing machine. b) describe the relationship between...
  19. S

    Will an 800 watt DC to AC inverter drain my car battery even when not in use?

    This is the specs of the inverter: Voltage In - 12VDC Voltage Out - 115VAC Continous POwer - 800W Peak - 1600W Out Frequency - 60hz Waveform - Modified Sine Wave No Load current - .75A Low Battery alarm and auto shutdown Overload and short circuit protection Input polarity reverse...
  20. S

    What is the flash wattage for a camera flash with a 765 µF capacitor at 345 V?

    The electronic flash attachment for a camera contains a capacitor for storing the energy used to produce the flash. In one such unit, the potential difference between the plates of a 765 µF capacitor is 345 V. (a) Determine the energy that is used to produce the flash in this unit. Using...
  21. T

    How to Measure Sunlight in Watts for a Room

    I need to measure the amount of sunlight that enters a room over a given period. I assume I'll need to get my hands on some device which can measure this, but in the meantime, is there a way to approximate how much light/energy enters the room at a given time? The best would be to get a Watt...
  22. T

    Interpreting J/s and J/(s^2): Watts & More

    Just trying to interpret some units here. If J/s is Watt, what does J/(s^2) tell me?
  23. T

    Explaining the concept of Watt to me

    A guy was explaining the concept of Watt to me, using a drawing of a machine that used 1 Joule per second, i.e. an oven. This one watt is now converted into heat, but excactly how much heat does 1 watt equal in terms of temperature? I'm not even sure if there is a relation, but if not, how is an...
  24. F

    Solving the Puzzle: Calculating Watts of "Wonderland's Watt

    hi, i have another question i can't get, the problem is: We want to boil one liter of water in a light thin-walled vessel. For this purpose, we start to heat water by an electric heater, with the label "500W. Made in Wonderland". However, after the temperature becomes 60*C, it stops...
  25. B

    Calculate the maximum current a 140 ohms, 1/2 watt

    I have looked thought all my notes and books and can not find the formal on how to do this question. I'm slowly going out of my mind any help would be great Calculate the maximum current a 140 ohms, 1/2 watt resistor can have flowing through it safely. Enter answer: mA Then...
  26. N

    Will this 2.2 watt solar charger charge my booster pack?

    Hey. I am not too knowledgeable on this topic so I was wondering if some of the knowledgeable folk here could help me out. Anyways, I have a 12 volt vehicle booster pack which is pretty discharged. There are no ratings on it except for the label that says "ES 2500." I am guessing that the 2500...
  27. C

    Can I Use a 60 Watt Bulb in a "40 Watt Max" Fitting?

    Gday, This is a very simple question and it should only take one sentence to answer. It's not worthy of these forums, lol, but despite my efforts I cannot find an answer through google. If a light fitting says '40 watt max' and I stick a 60 watt bulb in it, will that have any adverse...
  28. S

    Is a 120 Watt or 60 Watt bulb brighter?

    I had to do some homeowrk problems and i was hoping someone could just double check my answers... much appreciated. When you connect a 120 watt bulb and a 60 watt bulb in a parallel circcuit across a standard 120 volt outlet, which is brighter? the 120 watt bulb is brighter- right? because...
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