# circuits

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```					                                           Electric Circuits

Activity: Book Based Physics

Introduction:

When we walk into a dark room, our first reaction is to turn on the light switch.
This causes the light in the room to glow, which allows us to see. But, what had to
happen to allow the light bulb to glow? This lab will allow us to discover the answer.
All lights need a source of power to be able to glow. For most lights, this source
of power is called electricity. Electricity is made up of charged particles. These particles
are very small. These particles group together and flow from a negative charge to a
positive charge. This flow is called an electric current. But, this electric current needs a
path to follow. This path is known as an electric circuit. Electric circuits allow the
electric current to flow from the power source, to the light bulb and back again.
There are two different ways to classify circuits. The first way describes the
pathway of the circuit. A circuit can be either open or closed. An open circuit is broken
somewhere. It cannot transport the electric current. A closed circuit is unbroken. It
allows electricity to flow completely. The second classification deals with the number of
paths the electricity can use to create a closed circuit. The circuits in this classification
are the series and the parallel circuit.

Purpose:

This lab will demonstrate the different types of circuits. It will also have students
create and operate a switch.

Equipment and Materials:

5 Insulated wires: stripped on each end                 paper clip
2 small light bulbs                                     2 brass fasteners
2 small light bulb holders                              D size battery
piece of cardboard: 4 x 4 inch square                   tape
Safety:

   Always be cautious when around electricity. It can shock you very easily.
   Do not connect anything to your circuit that is not listed in the procedure.

Procedure:

Part 1: The closed circuit

1. Pick up the battery. Find the negative end. It is either not marked, or has a
minus sign on it.
2. Tape 1 end of the insulated wire to the negative end of the battery.

tape
Insulated wire, stripped
on the end

battery

3. Wrap the other end of the wire around 1 of the ends of the light bulb holder.
It should look something like this.

battery

Light bulb holder

4. Tape 1 end of a second insulated wire to the positive end of the battery.
5. Connect the other end of the wire to the other side of the light bulb holder.
6. Put the light bulb into the holder. What happened? Why?
7. Draw a picture of your closed circuit in the space below.

Part 2: The closed circuit with a switch

1. Disconnect the wire from the positive end of the battery.
2. Pick up the cardboard and the paperclip. Lay the paperclip down on the
center of the cardboard.
3. Put an X on the cardboard at each end of the paperclip. Label the Xs as #1
and #2.

X               X
#1              #2

4. Move the paperclip off the cardboard and pick up 1 brass fastener. Push the
fastener down through X #1.
5. Put the other brass fastener down through X #2.
6. Take the brass fastener out from X #1. Slip the fastener through 1 end of the
paperclip. Now, push the fastener back through X #1. It will look like this.

7. Flip the cardboard over so you can see the tails of the brass fastener.
8. Take the wire that was connected to the battery and wrap the stripped end
around the tails of the faster that went through X #1. Separate the tails.

9. Take a third wire that is not connected to anything else and wrap one end
around the tails of the second fastener. Separate the tails. It will look like
this.

10. Flip the cardboard back over.
11. Connect the end of the third wire to the positive end of the battery with the
tape.
12. Move the paperclip over until it touches the #2 brass fastener. What
happened? Why?

13. Move the paperclip off of the fastener? What happened? Why?
14. Draw a picture of the switch in the on position.

15. Draw a picture of the switch in the off position.

Part 3: The series circuit and parallel circuit

1. For this part you will need to work with another group.
2. Before you continue, choose which group is building a series circuit and
which group is building a parallel circuit.
3. Now, follow the directions below based on which circuit your group has
decided to do.

Series Circuit:
1. Disconnect the wire from the negative end of the battery.
2. Connect this wire to the second light bulb holder.
3. With a 4th wire, connect the other end of the second light bulb holder to
the negative end of the battery.
4. Put the second light bulb into the empty holder.
5. Turn the switch to the on position. What do you observe? Why?

6. End of Series circuit directions. Regroup and compare the two circuits.

Parallel circuit:
1. Turn the switch to the off position.
2. Connect a 4th wire to one end of the light bulb holder that was used for the
closed circuit. This creates 2 wires connected at the same place on the
light bulb holder.
3. Connect the 4th wire to the second light bulb holder.

4. Connect a 5th wire the same way you did with the 4th wire. Connect one
light bulb holder to the other.
5. Put the second light bulb into its holder.
6. Move the switch to the on position. What do you observe? Why?
7. End of Parallel circuit directions. Regroup and compare both circuits.

With both circuits together:

1. Put both circuits where both groups can see them.
2. With the switch on, remove one light bulb from both circuits. What happened
to the other light bulb in the series circuit? Why?

What happened to the second light bulb in the parallel circuit? Why?
Questions:

1. a. What is the major difference between the series and parallel circuits?

b. How could you tell this difference existed?

2. Why was a paper clip used in the switch?

3. Is it important to use insulated wires when using electricity? If yes, Why? If
No, Why not?
Electric Circuits
Teacher’s Notes

Lab Time: 40 minutes

Preparations:
Time: 10 –15 minutes

T: The insulated wires should be cut into pieces about 8 inches long. Then strip
about one inch of the insulation off of each end. Insulated wires are available
in many different styles and sizes. The only specification recommended is to
use wire that is at least 1/8 of an inch thick. This thickness is for easier
handling. Anything thinner is really fragile and hard to handle.

T: Do not use wrapped or insulated paperclips. The coating will not allow the
electric current to flow. The paperclips must be bare metal.

T: It is also recommended to have a few extra prepared wires ready for use. This
will prevent hold ups if a student looses or breaks a wire.

T: The piece of cardboard should be about a 4x4-inch square. This size is
recommended for easy handling. It can be altered based on supply.

T: Other batteries can be used. Ones that seem to work well are the 9V battery
and the large square 1.5V battery with the spring terminals.

T: Breakdown of Vocabulary:
closed circuit – a complete circuit, no breaks. Allows complete electricity
flow.
open circuit – a broken circuit. Allows no electricity flow.
series circuit – only 1 path for electricity to follow. If this path is broken the
circuit becomes an open circuit allowing no electricity to flow.
parallel circuit – there is more than 1 path for electricity to follow. If the path
is broken in certain areas, the current can still flow around the break. An
example of a passable break would be a blown light bulb.

V: The van can supply needed materials as requested.

Drawings of the circuits and the switch:

The Closed Circuit:
battery
Closed circuit with switch on:

Switch off:

Series circuit:

Parallel Circuit:

1. a. What is the major difference between the series and the parallel circuit?

The series circuit has only 1 path for electricity to flow through. The parallel circuit
has more than 1 path for the electricity to flow through.

b. How could you tell this difference existed?

In the series circuit, when 1 light bulb was removed the other bulb went out. In the
parallel circuit, when 1 light bulb was removed the other stayed on. It did not matter
which bulb was removed, the other still burned.

2. Why was a paperclip used in the switch?

Paperclips are metal, which is a good conductor. Conductors allow electricity to
flow through them. Insulators stop the electric flow.

3. Is it important to use insulated wires when using electricity? If Yes, Why? If No,
Why not?

Yes, the insulated wires carry the charged particles through the circuit. They also
prevent us from getting shocked, especially when working with stronger currents.

Considerations:
There are many ways to alter this lab. One way is to bring in Christmas lights.
One set wired in a series and the other in a parallel circuit. The students can then remove
a light bulb in the chain and determine which string is wired in which way. Another way
to change this idea is to use a stronger source and have the students’ figure out how many
light bulbs the electric current can flow through. Most students are amazed how far
electricity can travel. A third way to alter this lab is to build the series circuit with the
switch but do not put the paperclip in. Then have students determine which products are
conductors and which are insulators by placing these objects on both brass fasteners. The
conductors will allow the bulb to light and the insulators will block the electric flow
preventing the bulb from lighting.

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 views: 10 posted: 12/6/2011 language: English pages: 11