Electricity
4th grade Science
What is an electric
current?
A flow of electrical
charges
Important Fact
Electric current will
only flow through a
complete circuit.
Making a Circuit
• You need a path to carry the electricity.
This path along which an electric current
flows is a circuit.
• 3 basic parts of a circuit
– power source (ex. battery)
– load (a lamp or a bulb, etc.)
– connectors (ex. wires) They carry the electric
charges between the power source and the load.
Making a Circuit
• Many circuits have a switch.
– It turns the electric current on and off.
– Ex. the lights in a room turn on with a switch
• Closed Vs. Open Circuits
– The circuit cannot have any breaks or the
electric current can not flow.
– A closed circuit is complete and unbroken.
– An open circuit has breaks or openings.
Did you Know?
When a bulb burns out, a wire inside
of it breaks in two. This causes the
circuit to no longer have a complete
path. It is now an open circuit and
electric current cannot flow through
it.
Let’s try it!
Materials: power source (battery),
connectors (three wires), load (bulb),
and switch
Investigation: Create a closed circuit
that will allow the electric current to
flow.
Can you turn this complete,
closed circuit into an open
circuit?
Open the switch!
What is a series circuit?
• All electrical charges flow in the same
direction
• The parts are connected in one loop
• Electric current moves along one path
– current goes from power source to load then to
another load and finally returns to power source
[through wires]
• All of the parts are connected one after
another
Let’s try it!
Build a series circuit...
Materials: power source (battery),
battery holder, connectors (three
wires), 2 loads (bulb), and bulb
holders
Investigation: Create a series circuit.
Series Circuits
Let’s try it!
Build a series circuit...
Unscrew one of the light
bulbs.
Does the light bulb still
light up? Why or why
not?
Questions to Ponder...
• One bulb burns out in a series circuit. Will
current flow in the circuit?
• A string of small lights are an example of a
series circuit. If the first light goes out,
what happens to the others? What if the last
light burns out?
What is a parallel circuit?
• All electrical charges flow through more
than one path. These different paths are
referred to as branches.
– Some of the electric current flows through one
branch and some flows through another branch
Let’s try it!
Build a parallel circuit...
Materials: power source (battery),
battery holder, connectors (4 wires), 2
loads (bulb), and 2 bulb holders
Investigation: Create a parallel
circuit.
Parallel Circuits
Let’s try it!
Build a parallel circuit...
Unscrew one of the light
bulbs.
Does the light bulb still
light up? Why or why
not?
With a parallel circuit...
• If any branch of the parallel circuit breaks
or is removed, current will still flow through
the other branches.
• If the light bulb on one branch burns out,
the light bulbs on other branches will still
glow.
Did you know?
You can have a combination of a
series and parallel circuit. Many
circuits in electrical devices, even
circuits in your home, are
combination circuits!
What affects electric current?
• Voltage
–strength of a power source
–a power source with more
voltage can produce more
electric current
–measure in units called volts
What affects electric current?
• Resistance
– ability of a substance to oppose or slow down electric
current
– increasing the resistance of a circuit decreases the
flow of electric charges
– also allows electrical energy to be changed into other
forms of energy [Ex. light or heat]
– Very little resistance…copper wires-can carry a great
deal of electric current *CONDUCTOR
– Large amount of resistance…rubber-it is difficult to
make electric current flow through it *INSULATOR
Questions to Ponder...
• If you add bulbs to a series circuit, the
circuit has higher resistance. What happens
to the electric current in the circuit?
• If you decrease the resistance of a circuit,
what will happen to current in the circuit?
What is a short circuit?
• A path with almost no resistance
• It can stop the rest of the circuit from operating
properly.
• Can be dangerous!
–The wire heats up and may cause a fire.