In this video you’ll learn how to calculate the maximum load for you circuit breaker or fuse:

In this video we’ll show you how to easily calculate the maximum load for a fuse.

Let’s begin with the basic formula P = UI, in which P stands for power, U stands for voltage, and I stands for current.

Power is measured in watts, voltage is measured in volts, and current is measured in amps.

This means we can say the formula like this: Watts equal volts times amps.

Now let’s fill in some numbers.

We know that the voltage of US mains electricity is 120 volts.

The voltage of EU countries is usually 230 volts.

Then let’s look at wattage.

An old fashioned light bulb might use something like 40 watts. You can usually find the wattage printed somewhere on the item.

Here’s a more modern energy saving lamp. It only takes 23 watts. With these kinds of low wattage appliances, you’ll never really have a problem with the fuse size.

But our third example is a really powerful halogen, and this one will use up to 500 watts. If you have several of these turned on simultaneously, you might want to check your fuse size. So let’s use the wattage from this halogen in our example calculation. We’ll put in 500 for the power. Then let’s use the EU standard for the volts this time so put in 230 for the voltage. The current is X, because that’s the value we want to calculate. In other words, we want to know how big of a current our 500 watt lamp will produce with 230 volts of electricity.

So how do we solve this equation? We’ll this one is really easy: When we have something times X, we can divide both sides with that number to get only one x on the other side.

So we’re going to take 230, and divide the right side with it to produce one x.

Then we have to divide the left side with the same amount, so 500 divided by 230. That’s 2.17. So 2.17 equals X. Or we can say it the other way around, x equals 2.17. This means our 500 watt lamp has a current of 2.17.

Okay but what if we want to calculate it the other way around? What if we know we have a 10 amp fuse, and we want to calculate how many watts we can use with it.

So now watts is the x we want to solve. Maybe we’ll use the US mains voltage this time, so let’s put in 120 for the volts. The amps are ten, because that’s the fuse size we have. as you can see, this one is a really easy calculation. Simply multiply 120 with 10. This of course gives us 1200 watts as the answer. So we could essentially run two 500 watt lamps safely with a 10 amp fuse.

Thanks for watching and see you next time on!



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