Electric toasters
Last updated: September 18, 2007.
Yum, toast! What could be better than a
nice crisp piece of buttered toast first thing in the morning? If you don't like standing by the
stove watching and waiting for your bread to turn brown, an electric
toaster could be just the thing for you.
You probably know that a machine like
this turns the power of electricity into heat that can cook your bread
in a jiffy. But you do you know how the electricity that flows into the
toaster gets transformed into a totally different kind of energy? Let's
take a closer look inside.
Photo: A typical electric toaster.
Turning electricity into heat
Energy is a kind of magic, invisible
substance that lets you do things. Heat is one kind of energy and
electricity (generated by power plants
and stored inside things like batteries) is another. You can't make
toast by standing a slice of
bread on top of a battery—and nor should
you try! But you can make toast with electricity if you use an electric
toaster. So what's the difference?
If you've ever looked down inside a toaster, you'll have noticed
rows of glowing red wires facing the bread. When electricity
flows through these wires, they get hot and then fire their heat toward
the
bread like dozens of miniature radiators. You must
never ever touch these wires (which
are called filaments or
elements), either with your fingers or with any other object, because
they are dangerously hot and carry large electric currents that could
zap through your body, electrocute you, and kill you.
When electricity flows through a wire, energy is transmitted from
one end of the wire to another. The movement of energy is a bit like
water flowing down a pipe. The electrical energy is carried down the
wire by electrons, the tiny particles inside the atoms of metal that
make up the wire. As the electricity flows, the electrons jostle about
and collide with one another, and with the atoms in the metal wire,
giving off heat in the process. The thinner the wire, and the greater
the electric current, the more
collisions happen and the more heat is generated.
Heat and light
Heat is not the only thing that's produced when electricity flows
down a wire. If the wire is thin enough, and providing it's not covered
with plastic insulation, its temperature
may rise so much that it glows
red hot. What's happening here? If the wire is glowing, it must be
giving off light. The atoms inside the metal wire are being heated up
by the electrons flowing through it. They're absorbing some energy as
heat, becoming unstable, and then giving off some of the energy as
light to try to become stable again. (See our article on fluorescent lamps for more
details of how atoms produce light.)
Photo: Yum, toast!
Old-fashioned electric lamps use this trick to produce light. Inside
their large glass bulbs, they have a filament made from an incredibly
thin piece of coiled wire. When electricity flows through the filament,
it becomes extremely hot and produces both light and heat. Making light
by heating something up in this way is called indandescence.
Incandescent light bulbs waste most of the electrical energy they
consume. About 90 percent of the electricity in a light bulb like this
turns immediately into heat, which is incredibly wasteful.
That's why many people are now switching over to energy-efficient fluorescent
lightbulbs, which produce just as much light without producing heat.
In a toaster, the opposite is the case: we're obviously much more
interested in producing heat and the small amount of light produced by
the glowing filaments is wasted energy.
It's elementary
Toasters and incandescent electric lights are just two examples of
many household appliances that make heat when electricity flows through
them. Electric showers, coffee machines,
radiators, fan heaters, hair dryers, hair curlers, irons, tumble
dryers, washing machines, and
cookers
work in a very similar way. (Microwave
ovens, however, work in a completely different way, using
electromagnetic radiation to zap heat into water molecules inside your
food.)
Appliances such as showers and kettles that heat up water with
electricity have to do it in a safe way to ensure they don't
electrocute you. Instead of using a thin bare wire (like the ones you
can see inside your toaster), they use a different kind of heating unit
called an element, which has the bare wires safely contained inside it.
The element is the shiny curved piece of metal you can see at the
bottom of an electric kettle. Don't ever attempt to
touch it because you'll burn or otherwise injure
yourself.
Photo: Left: The glowing elements inside a
toaster.
Right: You can clearly see the coiled
electrical element at the bottom of this kettle. As electricity flows
through the thick metal coil, electrons inside make the metal heat up
and that heat is rapidly passed onto the water inside the jug.
How do toasters know when to switch themselves off?
Most toasters have electrical or mechanical devices on them that
switch off the electricity after a certain time has elapsed. So if
you set the toaster to cook your bread more, you're actually just
leaving it on for longer. When the timer switches off, it activates an
electric switch that releases a spring and pops up your toast. It's
easier to get your toast out if it pops up. It's safer too because the
inside of the toaster is usually much too hot to be reaching into.
Go shop
