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Watt facts for kids

Kids Encyclopedia Facts

The watt (symbol: W) is a unit of power in the SI system. It is named after a scientist named James Watt. He lived from 1736 to 1819.

The watt helps us measure how fast energy is used or produced. Imagine a light bulb that uses one watt. This means it changes one joule of electrical energy into light and some heat every second. So, the watt tells you how much energy an appliance uses each second. The more watts an appliance has, the more energy it uses per second. This is why a higher-watt appliance often works faster.

A watt is the same as one joule per second (J/s). You can also think of it as one volt ampere (1 V·A). A watt is also about 1/746 of a horsepower. The power of a light bulb is measured in watts. For example, LED lights use much less power. A small LED might use only 0.015 watts (2.0×10−5 horsepower), which is also called 15 milliwatts.

When you have 1000 watts, it's called a kilowatt (kW). This is 103 watts. In many places, your electric bill is based on how many kilowatt-hours you use.

A megawatt (MW) is 1,000,000 watts (106 watts). This unit is used to describe the large amounts of electricity needed for a big town. Even bigger is a gigawatt, which is 1,000,000,000 watts.

Power, work, and time are all connected. Here are some simple formulas to help you understand:

  • Power = Work ÷ Time
  • Work = Power × Time
  • Time = Work ÷ Power

Solving a Power Problem

Let's try an example! If a light bulb uses 100 watts (100W) and you have 1000 kilojoules (1000kJ) of energy, how long can the light bulb stay on?

First, remember that 1 kilojoule is 1000 joules. So, 1000kJ is 1,000,000 joules (1,000,000J). We need to find the time, so we use the formula: Time = Work ÷ Power.

  • Time = 1,000,000J ÷ 100W
  • Time = 10,000 seconds

Now, let's change 10,000 seconds into hours, minutes, and seconds:

  • 10,000 seconds is 166 minutes and 40 seconds (since 10,000 ÷ 60 = 166 with a remainder of 40).
  • 166 minutes is 2 hours and 46 minutes (since 166 ÷ 60 = 2 with a remainder of 46).

So, the light bulb can stay on for 2 hours, 46 minutes, and 40 seconds.

See also

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