Why Do Microwaves Take Longer With More Food?

You happen not to be the only one in this soup wondering why microwaves take longer with more food.

And I’m confident we aren’t the only people in this, as many will also be wondering and wanting to find out why it happens that way. Let’s get to find that out right here.

In microwave operations, microwave radiation is produced by the magnetron.

This radiation is absorbed by the food or substance in the microwave and causes the water molecule to vibrate, generating heat energy, which tends to heat the food.

So normally, the greater mass of food will require more heat energy to heat it.

But the amount of microwave radiation produced is the same irrespective of the amount of food; hence, the amount of heat available to heat the food will be lesser, causing the heating rate to slow.

And that will require a much longer time for the food to be fully heated up as expected.

So since the amount of heat produced is the same, smaller food will get heated up at a faster rate than that more food.

This is the same when you heat two of the same food in the microwave. It takes much longer than heating just one.

Why Does Cooking Two of the Same Food in a Microwave Oven Take Longer Than One?

With the same mechanism as how the microwave operates, the generated heat from the vibration of the water molecules in the food is shared among the two separate food.

And in so doing, the heat which is supposed to heat a single one of them will now be divided for the two food—making the time for fully heated food double up.

Having a slice of pizza in the microwave will heat faster than having two slices of pizza simultaneously. Let’s assume I have two plates of pizza slices in the microwave.

As it is powered on and running, the amount of microwave radiation is the same amount that would’ve been produced if only one slice were in the microwave.

The reflection of this microwave radiation in the inner part gets absorbed by the two pizza slices, which causes vibration leading to heat generation.

The heat energy produced at the time will be shared among the two slices of pizza in the microwave.

This heat energy shared among these two slices would’ve been for only one if it was the only slice.

Why Does Cooking Two of the Same Food in a Microwave Oven Take Longer Than One
Why Does Cooking Two of the Same Food in a Microwave Oven Take Longer Than One

But in this scenario, it will be shared with the two pizza slices. This will then reduce the rate at which the pizza will be heated.

Hence, the time taken to heat will be prolonged to have a fully heated pizza. So it takes much longer to cook two of the same food in the microwave at a time.

What Happens If You Run a Microwave with Nothing in It?

In the workings of the microwave, it’s the microwave radiations that get absorbed by the food or substance in the microwave, causing the water molecule to vibrate to generate the heat energy which tends to cook or heat the food.

An electron tube name magnetron produces this microwave radiation. When there’s nothing in the microwave but powered to run, the radiations will be redirected back to where they came from; that’s the magnetron.

The magnetron will then absorbs the radiation just as food would’ve done. Continuous absorption of microwave radiation tends to damage it.

And without the magnetron, there’s no microwave radiation to be produced. Hence the microwave oven can’t function.

It’s similar to the microwave or magnetron when food without water molecules is continuously placed in the microwave.

Though there’s food, the microwave radiation will still be redirected back to the magnetron since the waves don’t react with the food in its solid state but rather the water molecules.

What Happens If You Run a Microwave with Nothing in It
What Happens If You Run a Microwave with Nothing in It

What Happens if the Magnetron Damages?

The magnetron is the key part of the microwave as far as its functioning is concerned, and you know what that means. Without it, the microwave won’t be able to operate as it’s expected to.

There’s no problem when the microwave runs for a few seconds without anything in it. But to prolong it, that’s where the problem lies.

To sense when the magnetron is deteriorating, you will notice a burning smell from the microwave.

Now, you should do well not to run the microwave with nothing in it. And talking of its damage, once it’s fully damaged, it won’t be able to produce microwave radiation again. Hence nothing placed inside it will get to be heated or cooked.

Is it Safe to Boil Only Water in the Microwave?

As we all know, water is a needed factor in using microwaves. There’s no way you can have microwaved food or substance without the existence of water in it. It does happen, though, but that isn’t the best.

But the question is, is it advisable to boil only water in the microwave? Health-wise, is it safe and convenient to use water heated or boiled with the microwave. No research has been able to prove the negative effect of microwaved water.

What you should know and take good note of about boiling water in a microwave is that it can cause severe burns when not handled well.

Water boils at 100°C (212°F), and in the boiling process, bubbles are formed from beneath as the water converts to a gas (steam).

And that’s not the case with microwaved water. With that, there are no bubbles, but the water tends to superheat; it boils above the normal boiling point.

And when that happens, as soon as the water is taken out of the microwave and is agitated, it begins to boil at once. When less care is taken might cause some harm to the person handling it or around it.

In some instances, once the cup or whatever the water is in is taken out of the microwave, it explodes. And this is caused by the sudden swap of temperature, that’s the superheating state to a normal state.

To avoid an explosion, you should always avoid heating water for long minutes. You should also desist from using smooth containers for boiling the water.

You can use an old cup or mug with some little scratches on the inner part. The container shouldn’t just be smooth, and you’re good to go.

Is it Safe to Boil Only Water in the Microwave
Is it Safe to Boil Only Water in the Microwave?

You should inculcate the habit of stirring your water when it’s done boiling while it’s still in the microwave. And in so doing, keep the face away from it. Use a much longer object to stir to avoid taking the face near it.


The more food is in the microwave, the longer it will take to get it fully heated up or cooked.

The slow rate causes it takes to get the food heated or cooked since the mass of food to be heated is greater than the same amount of microwave radiation produced.

It’s these waves that get absorbed by the food and get it heated. So the waves are, in a way, limited in their operations—the same way when you tend to cook two of the same kind of food in the microwave.

With this, the waves are divided among the two separate food, which will also slow down the heating or cooking rate, prolonging the heating or cooking time.

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