1. Electricity
4th grade Science

2. What is an electric current?
A flow of electrical charges

3. Important Fact Electric 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. Closed Vs. Open Circuits
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. 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.

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. 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.

11. Series Circuits

12. 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?

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. 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.

16. Parallel Circuits

17. 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?

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 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

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.