Electricity 4th grade Science What is an electric current? A

1
Electricity
4th grade Science
2
What is an electric current?

• A flow of electrical charges

3
Important FactElectric current will only flow
through a complete circuit.
4
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.

5
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.

6
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.

7
Lets 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.

8
Can you turn this complete, closed circuit into
an open circuit?

• Open the switch!

9
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

10
Lets 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.

11
Series Circuits
12
Lets try it!Build a series circuit...

• Unscrew one of the light bulbs.
• Does the light bulb still light up? Why or why
  not?

13
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?

14
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

15
Lets 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.

16
Parallel Circuits
17
Lets try it!Build a parallel circuit...

• Unscrew one of the light bulbs.
• Does the light bulb still light up? Why or why
  not?

18
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.

19
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!

20
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

21
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 resistancecopper wires-can carry a
  great deal of electric current CONDUCTOR
• Large amount of resistancerubber-it is difficult
  to make electric current flow through it
  INSULATOR

22
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?

23
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.