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Home & Kitchen

How does a toilet flush? A European toilet flushes by releasing a tank of stored water through the bowl and trap, then a float valve refills the tank. A water seal in the trap blocks sewer gas. How does a microwave heat food? A small airless tube in the oven, with a hot wire, magnets and a copper ring, makes invisible waves that a metal channel guides into the box. The metal walls and the net in the door keep them bouncing around inside. The waves make the water in food twist back and forth billions of times a second, and that jostling is heat. The outer layer heats first and the warmth then spreads inwards. How do a fridge and a heat pump move heat? A fridge doesn't make cold. It moves heat out of the box with a loop of pipe and a fluid that boils very easily: a pump squeezes the gas so it gets hot, a hot coil gives the heat away, a tiny gap makes the fluid ice cold, and a cold coil soaks up heat again. A heat pump is the same loop, with the cold coil outdoors and the hot coil heating the house. How does yeast make bread rise? Yeast is a tiny living fungus. In bread dough it eats sugar and gives off gas. Stretchy strands in the kneaded dough trap that gas in tiny bubbles, the bubbles grow and push the dough up, and the oven makes them swell once more before the dough sets around them.