Page 61 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

Technology

Why do kettles

sometimes whistle?

he high-pitched whistling sound
produced by a classic stove kettle is
designed to alert you when the water inside
reaches the boiling point. The actual
whistling sound is created when built-up
steam is forced to escape through the steam
whistle, which is attached to the end of the
spout. The steam whistle features two
narrow holes that restrict the flow of air. The

first opening contracts the steam as it enters

and creates a concentrated jet of steam. The
jet, however, loses stability as it passes
through the whistle towards the exit hole,
much like a jet water from a hose will begin
to break into droplets after a certain
distance. This means that the steam can’t
flow steadily out of the whistle and will

instead bounce off the whistle wall, creating
vortices. It is these vortices that produce the
well-known whistling sound of a kettle.

Does charging your

phone overnight kill

the battery?

o. Overnight charging is actually the scenario phones are
N designed for. The charging circuit in your phone will cut
out when the battery reaches maximum capacity. So you
can’t overcharge your phone, no matter how long you leave it
plugged in. If you never unplug your phone from the wall, you
will eventually lose battery capacity, though. That’s because
lithium batteries slowly degrade if they are held at maximum
charge for long periods. After an entire year at full charge, a
battery will lose 20 per cent of its maximum capacity,
compared with just four per cent after a year at half charge.

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