Circuits
•A circuit always needs a power source, such as
a battery, with wires connected to both the
positive (+) and negative (-) ends.
•A circuit can also contain other electrical
components, such as bulbs, buzzers or motors,
which allow electricity to pass through.
•Electricity will only travel around a circuit that
is complete, i.e. has no gaps.
Switches
• When a switch is open (off), there is a gap in the circuit.
Electricity cannot travel around the circuit.
• When a switch is closed (on), it makes the circuit
complete. Electricity can travel around the circuit.
Changing circuits
• Adding more batteries to a simple circuit
will make a bulb brighter.
Changing circuits
Adding more bulbs to a simple circuit
will make the bulbs dimmer.
Electrical conductors
• Some materials let electricity pass through them
easily. These materials are known as electrical
conductors.
• Many metals, such as aluminum, copper, iron and
steel, are good electrical conductors.
• That is why the parts of electrical objects
that need to let electricity pass through are
always made of metal!
Electrical insulators
• Some materials do not allow electricity
to pass through them. These materials
are known as electrical insulators.
• Plastic, wood, glass and rubber are
good electrical insulators.
• That is why these materials are often
used to cover materials that carry
electricity!
http://www.bbc.co.uk/schools/ks2bit
esize/science/tests/changing_circui
ts.shtml
• http://www.bbc.co.uk/schools/ks2bitesize/s
cience/tests/conductors.shtml
http://www.bbc.co.uk/schools/ks2bitesize/science/tests/magnets_springs.shtml
Magnets
• When two magnets are close, they create
pushing or pulling forces on one another.
• These forces are strongest at the ends of the
magnets. The two ends of a magnet are
known as the north pole and the south pole.
• If you try to put two magnets together with
the same poles pointing towards one
another, the magnets will repel (push away
from) each other.
• If you put two magnets together with different
poles pointing towards one another, the
magnets will attract (pull towards) each other.
Some magnets are stronger than others.
Strong magnets will create bigger pushing or pulling forces than weak magnets.
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Magnetic materials
Magnets can attract other magnets but they can also
attract magnetic materials.
Magnetic materials are always metals but only a few
metals are magnetic.
Iron IS magnetic, so any metal with iron in it will be
attracted to a magnet. Steel contains iron, so a steel
paperclip, for example, will be attracted to a magnet.
Most other metals, for example aluminum, copper and
gold, are NOT magnetic. An aluminum drink can, for
example, will not be attracted to a magnet.
• Objects usually have equal numbers of positive
and negative charges, but it isn't too hard to
temporarily create an imbalance. Have you ever
received a shock after walking across a carpet?
As your feet shuffle across the carpet, they pick
up extra electrons. Those electrons can't wait
for you to touch something metal. As soon as
your hand is close, they jump off with a shock
and a spark of static electricity.
• Atoms, the basic building blocks of matter, are
made of three basic components: protons,
neutrons and electrons. The protons and
neutrons cluster together to form the nucleus,
which is the central part of the atom, and the
electrons orbit about the nucleus. Protons and
electrons each carry a charge. Protons carry a
positive charge while electrons carry a
negative charge. Neutrons are neutral - they
carry no charge at all.
• A continuous flow of electrons creates an electric current. Materials
that allow electricity to easily flow are called conductors. Electrical
wires are made of metal because metal is one of the best
conductors. One type of metal, copper, is most often used for
electrical wires. Materials that do not allow electricity to pass easily
through them are called insulators. Rubber, glass, plastic, cloth,
and most non-metallic materials are poor conductors of electricity.
This is why electrical wires are covered in rubber, plastic, or cloth.
Electricians even wear rubber gloves when they are working with
electrical wires. This does not mean that electricity cannot pass
through insulators or any other material. If you give any object
enough voltage (the force or push behind the flow of electricity),
then that object will conduct electricity. Resistance slows down the
flow of electrons is as it travels along the passageway of the wire.
For example, longer electrical wires pose a greater amount of
resistance to electricity than shorter wires. This is because the
electricity has farther to travel.