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Electric Circuits Honors Answers
An Electric Circuit is defined as the path followed by an electric current from a power source through
devices that use electricity and then back to the source. Today, you will be experimenting with the
interactions between the components found in an electric circuit.. For every interaction that takes place, it is
important to know WHICH variables influence that interaction. It is also important to know HOW they
influence that interaction. With electricity, it is important to understand that the interaction occurs when a
SOURCE of electricity is connected to a device that uses or needs electricity in order to operate.
KEY Questions you should be able to answer at the end of the activity:
1.
What are the defining characteristics of an electric-circuit?
2. What are the variables (both TEST/Independent and OUTCOME/Dependent) that influence the
electric-circuit?
Look at the center table, where Mrs. Twedt is demonstrating. This circuit has TWO bulbs glowing within
the circuit.
Think: If you unscrewed one bulb and remove it from its socket, what do you think would happen to the
other bulb?
Discuss your thoughts with your group/class.
Before we begin…. Make a flow map showing the energy transfers in a
circuit:
Cell
Wires
Bulb
Chemical
Electrical
Thermal and Electromagnetic
A circuit is a closed system. What does this mean?
A closed system means it is not likely anything is flowing in or out….what’s there is there except for the energy
transferring in to make the system function, and some energy out (as unusable energy).
How would the law of conservation apply here? Energy cannot be created nor destroyed, only changed or
transferred. SO the energy put into the closed system is simply transformed into other energy types as it flows
in a circle through the circuit!
You will be performing a series of FIVE explorations in order to address the two key questions below.
When asked to DRAW your circuits, please use the following universal symbols for each component of the
circuit.
Component
Cell
Illustration
Universal Symbol
Wire
Bulb in Socket
Switch (Closed)
Switch (Open)
Ammeter
Voltmeter
Motor
Buzzer
**In these activities, we will use the term “cell” to refer to one D-Cell (1.5 V (volts)). To us, this is a
“battery.” However, scientists define a “battery” as a device that combines MORE than one cell.
Exploration 1: WHAT makes an electric circuit complete?
Materials:
3 cells
3 cell holders
3 bulb holders
3 bulbs
1 switch
4 hook-up wires
several metal and non-metal objects
Procedure:
1. Mount one cell in one cell holder.
2. Screw one bulb CAREFULLY into one bulb holder.
3. Use two hook-up wires to connect the cell (in holder) to the bulb holder to make the bulb light up.
 This closed LOOP is called an electric circuit. When the bulb is lit, your circuit is closed, and
therefore complete!
4. Add a switch to the circuit so you can turn the bulb on and off (also so you don’t drain the
batteries!!!). *You will need an additional hook up wire.
5. Raise your hand (#2s) to have Mrs. Twedt check your circuit.
6. Draw a picture of the circuit (when the bulb is lit) below. *Make sure to use the correct symbols!
Label it.
7. Look carefully at how everything is connected.

How many connections are there to each component in the circuit? 2 per component

How do you know your circuit is closed/complete? The
light turns on!
Chemical energy in the battery – Electrical energy through
the wires once the circuit closed – Thermal energy in the
bulb (and throughout the circuit as unused) Electromagnetic energy (LIGHT)!
Exploration 2: What types of materials are necessary for an electric-circuit?
In the last exploration, you found that if you hooked up a circuit like the one
here and closed the switch, a bulb lit. This is the evidence that an electriccircuit is complete.
Procedure:
1. Add another hook up wire and attach a nail to your circuit like the
picture to the right.
2. Close the switch.
3. Record what happened (whether the bulb lit up) in the table below.
4. Repeat steps 1-3 with the materials listed in the table.
5. Define the vocabulary listed below the table.
6. Determine the correct classification for each object in the table
(Insulator or Conductor).
7. Answer final question.
8. Raise your hand (#2s) to have Mrs. Twedt check your table. *Don’t
clean up yet!
Table 1: Tested Materials in an Electric Circuit and how they interact with the Circuit
Material
Interaction—Does the bulb
Insulator or Conductor
(Do NOT do this during the testing…instructions will be given)
glow? (Yes or No)
Iron nail
Yes
Conductor
No
Insulator
Yes
Conductor
No
Insulator
Yes
Conductor
No
Insulator
Yes
Conductor
No
Insulator
No
Insulator
Paper
Nickel wire
Plastic
Copper wire
Magnet
Aluminum wire
Glass
Wood
*Must be a school supply and MUST not be attached to you or your team members.
Define Insulator: Does not easily allow the flow of electrons (electricity)
Define Conductor: Easily allows the flow of electrons (electricity)--*Copper is the BEST conductor of
electricity. Nickel is actually not a great conductor, but still is a conductor.
Examine the data table and complete: In order for an electric-circuit to be complete, the type(s) of material
that must be included in the circuit is (are) Metals-CONDUCTORS. The evidence is THE LIGHT IS ON!
* Don’t forget about the existence of semiconductors! –Found in
LED lights, and other new technology.
Next, since you didn’t clean up (according to step 8).
9. Remove the light from your circuit.
10. Take copper wire and wrap it around the nail from this
station like the picture to the right.
11. Close the switch.
12. Set out the pile of paperclips to be near this circuit.
13. Move the nail to paperclip and observe what happens.
14. Record your data.
15. Add a cell to your circuit.
16. Repeat steps 13 and 14.
17. Repeat step 15.
18. Repeat steps 13-15 until data table is complete.
Table 2: The number of cells affects amount of magnetic force in an electromagnet
Number of Cells
Number of paperclips picked up by nail.
1
3
6
10
17
2
3
4
What did you create? An Electromagnet/Temporary Magnet
Brainpop---Electromagnet is extra credit and will help with this!
Describe what happened here: Electricity magnetized a nail.
What did the flow of electrons through the circuit do to the atoms in the FERROMAGNETIC nail?
*Include the word DOMAIN.
There are many domains, all pointing any which way, in a piece of iron. In a magnet, these
domains are all lined up together, to produce a strong magnet.
Random
This is the nail before the circuit was closed
Aligned
This was the nail after the circuit closed and electricity
flowed.
The basic principle of electromagnetism is that moving electrons
have a magnetic field. When the circuit was closed, electrons
flowed from the negative end of the battery through the wires,
including the copper wire (a STRONG conductor). In the
ferromagnetic nail, the magnetic domains (atoms) were
directionally scattered (see above “random” image) until the
electrons flowed through. Once this happened those domains
became aligned along with the flow of electrons (see above
“Aligned” image. Once the magnetic domains were aligned, the
iron nail became a magnetized and was able to attract the
ferromagnetic paperclips.
Write a conclusion that would include a potential hypothesis (look at your
variables above! ITMLX DORRY and include that relationship and data!).
If the number of cells increases, then the number of paperclips the
electromagnet can pick up will also increase because there will be
more electric current flowing through the circuit creating a stronger alignment of the domains
within the ferromagnetic nail. This is shown by one cell picking up 1 paperclip, whereas 4
cells picked up 7 paperclips.
Exploration 3: How can you hook up more than one bulb to a cell?
Procedure:
1. Hook up one cell and two bulbs in a single loop. Use as many wires as you need.
 This is called a single loop circuit OR a SERIES circuit.
2. Raise your hand (#2s) to have Mrs. Twedt check your circuit.
3. Draw a picture of this circuit below using the
correct symbols and label it.
*Both Bulbs SHARE the current from the cell.
4. Unscrew one of the bulbs from its socket.
5. Leave the other bulb alone.
6. Answer the following question: What happens to the bulb that is left in the circuit? It turns off. The circuit
has been broken/opened.
7. Replace the bulb that you unscrewed (make sure your circuit is open so you don’t drain the battery).
8. Use more hook up wires, if necessary, and see if you can find another way to connect these components by
putting each bulb in a separate loop to the cell.
 This is called a multi-loop circuit or a PARALLEL circuit.
9. Raise your hand (#2s) to have Mrs. Twedt check your circuit.
10. Draw a picture of this circuit below using the correct symbols and label it.
The bulbs each have their own path
to the cell. They do not need to share
the electric current, they pull their
own from the cell.
11. Unscrew one of the bulbs from its socket.
12. Leave the other bulb alone.
13. Answer the following questions: What happens to the bulb that is still in the circuit? It stays lit!
Why do you think your answers differed between the two circuits with the removed bulbs (steps 6 and 13)?
In the series circuit, there is only one path for the electric current to flow, so all components
must share the electricity. In the parallel circuit, there is one path PER component, so each
light has its own current. No sharing necessary, though more current is pulled from the
battery.
Exploration 4: If the number of cells in the circuit increases, what happens
to the brightness of the bulb?
Procedure:
1. Hook up two cells and one bulb in a single loop (series) circuit. *Make sure you connect the positive terminal
of the cell to the negative terminal.
2. Raise your hand (#2s) to have Mrs. Twedt check your circuit
3. Answer the following question: Is the bulb in the two-cell/one-bulb circuit brighter than, dimmer than or
equally as bright as the bulb in the one-cell/one-bulb circuit in exploration 1? Brighter
4. Add an additional cell and hook up wire, making your series circuit (still all in a loop) have three cells and one
bulb.
5. Answer the following questions:
a. What happens to the brightness of the bulb when additional cell is added to the
circuit? As each cell is added, the brightness of the bulb increases.
b. In Exploration 4, what is the TEST Variable (Independent)? Number of cells
OUTCOME Variable (Dependent)? Brightness of the bulb
2 Constants? Number of connections per component, Type of circuit (series)
Write what the hypothesis SHOULD have been, if we wrote it at the beginning
of this exploration.
If the number of cells in a series circuit is increased, then the brightness of the
bulb will increase because there would be more voltage available (from the
cells) so more current can flow (current x voltage = power! …the bulbs have
more power).
Exploration 5: If the number of cells in the circuit increases, what happens
to the amount of electric current in the circuit?
Remember (from the video):
Electric Current (Amps) = Flow of electricity (how much or many negative charges or electrons in motion)
Voltage (Volts) = The amount of electric potential (The “pressure” pushing the electrons along). *In the US,
the outlets in our homes deliver 120 volts each.
Resistance (Ohms) = A material’s tendency to resist the flow of charge (current).
Here is an example to help you understand. It refers to running water through a hose:
 Electric Current is like water flow rate, the “volume” of electricity that flows (measured in amps).
 Voltage is like water pressure, sort of the driving force “pushing” the electricity (measured in volts).
 Resistance is like the size of the hose (diameter) that allows flow (measured in ohms).
If there is no voltage (no pressure), there will not be any electrical current flowing (no water moving) even if the
resistance is zero (largest, widest hose known). BUT, it also works the other way: you have very high voltage (high
pressure), there may not be any electric current (no water flow) because the resistance is too high. ( hose too skinny).
**Please note: In referring to electric current, it does not begin in one place, like water coming down a hose
once you open the faucet; rather the flow of electric charge occurs simultaneously, all together/at the same time,
around the circuit.
Electric circuits are often described approximately by Ohm’s Law which states that the total voltage across the circuit
is equal to the total current of the circuit multiplied by the total resistance of the circuit (measured in OHMS/Symbol
is R). To summarize, Ohm’s law is Voltage = Total Current times resistance (V=IR).
EASY way to always remember:
Starting from any section of the triangle, this can be read in any direction you
like – clockwise, counter-clockwise, top to bottom or bottom to top – and it will
always provide you with the calculation you require. From this, we conclude
that; Current equals Voltage divided by Resistance (I=V/R), Resistance equals
Voltage divided by Current (R=V/I), and Voltage equals Current times
Resistance (V=IR).
Procedure:
1.
Write a hypothesis about the relationship between the number
of cells and the amount of electric current (your circuit is a single loop-series-circuit with one bulb).
*Make sure you discuss.
If the number of cells in a series circuit is increased, then the amount of electric current
will increase because there would be more voltage available (from the cells) so more
current can flow through the circuit.
**You will be using a computer simulator (a program that models experiments with as many
constants as possible) to test your hypothesis. Since the simulator holds most everything
constant, allowing you to isolate an independent variable to see how it affects a dependent
variable, we can say that the tests performed simulator are Valid. There is also minimal
human error involved, so the simulator is Accurate. This means that there is no need to
calculate best values or uncertainties….we aren’t uncertain about anything! We will be
getting the same answers over and over because this simulator was programmed with real
data from MANY explorations. *REPEATABLE! Therefore, the tests performed on this
simulator are Reliable.
**We could also have someone else perform this experiment and achieve the same results. =
Replicable.
Replicable and Repeatable = Reliable.
This simulator uses an ammeter to measure the amount of electric current. The unit common to the ammeter
is the milliampere (mA).
Below are the circuits you will build and test:
2. Acquaint yourself with the computer simulator (found on www.mrs-twedt.com *resources). Play
around a bit with it in order to get used to it.
3. Build your circuits to match those shown above.
4. Record the value of the ammeter readings for each of the four circuits when the simulator is run and the
switch is closed.
Table 3: The measure of the amount of Electric Current vs. Number of cells
Number of Cells
Amount of Electric Current (mA)
1
.90
1.80
2.70
3.60
2
3
4
5. Answer the following questions:
If you were to graph this data, what would you put on the X –Axis?
(Left)
If you were to graph this data, what would you put on the Y-Axis?
Number of Cells
ITMLX
Amount of Electric
Current (mA).
DORRY (Right)
*This shows me that you know your variables!
6. Complete the conclusion below:
If the number of cells in a circuit increases, then the amount of electric current
increases.
My evidence for this is (this is supported because) in the circuit with just one cell, .90
mA were measured. When the circuit increased to 2 cells, the current measured 1.80
mA; 3 cells = 2.70 mA; and with 4 cells in the circuit 3.60 mA of current moved
through the circuit.
Summarizing the Explorations/Experiments:
Last week, you learned about static electricity. The concepts you learned then can be applied and extended to
understand circuits. One end of a cell is positively charged (+), the other end of the cell is negatively charged (-). The
wires of the circuit and the bulb contain both + and – charges. Only the - charges (electrons) can move through the
conducting wires and bulb. The + charges (protons) do NOT move. When the circuit is closed (complete), the + end
of the battery attracts the – charges (electrons) in the wires and the – end of the battery repels the – charges. This
causes the negative charges to move through the circuit in the direction from the – side of the battery to the +
(OPPOSITES Attract!). As the – charges enter the + end of the battery, the same number of – charges leave – side of
the battery….causing continuous flow around the circuit! This flow of charges = electric current.
Coming to a Conclusion:
1. At the beginning of the Exploration, you were told you would eventually need to answer the following:
What are the defining characteristics of an electric-circuit? In order to answer this question
thoroughly, you simply need to answer the following:
What are the basic components of an electric-circuit? Cell, wires, and a receiver (bulb, buzzer, motor,
etc).
How are the objects connected together? In a loop (single loop-series, or muli-loop-parallel, but it must
be a complete (closed) “circle” with wires (conductors).
What is the evidence that an electric-circuit has been completed/closed? The receiver turns on (light,
buzzer, motor)….energy flows.
2. The second question from the beginning of the exploration was:
1. What are the variables (both TEST/Independent and OUTCOME/Dependent) that influence the
electric-circuit?
Think about everything you changed throughout this activity in order to see what occured.
What were some of the variables changed on purpose? For each test/independent variable you list, state
the outcome/dependant variable (affected by that change).
IDV
# of cells
Type of circuit
(Number of loops or paths)
DV
Brightness of Bulb
Amount of electrical current (amps)
Amount of electrical current (amps)
Whether or not bulb stays lit
3. You can buy two types of holiday lights.
Type A—When you plug in the strand of lights, one bulb goes out so the rest of the strand goes out.
Type B—When you plug in the strand of lights, one bulb goes out but the rest stay lit.
One of these types is connected all in a series with the electrical source; the other type is connected in a
parallel circuit with the electrical source.
Which type, A or B, is connected in series? A
How did you know? When one bulb goes out, the rest go out because the path has been broken.
Which type is connected in parallel? B
How did you know? All the other lights stay lit because each light has its own path to the source (cell).
4. Consider how your electrical devices are connected together at home. Suppose you have a room with two
different lamps.
Do you think the lamps are connected together in series or in parallel? Parallel
How do you know? When you turn one lamp off, the other stays on.
5. Using Ohm’s Triangle:
Example:
If a circuit has a current of 2 amperes, and a resistance of 1 ohm, what is the voltage?
V = 2 amperes (I) x 1 ohm
The circuit has a voltage of 2 V.
You try:
If a circuit has a voltage or 4 V and a current of 5 amperes (I), what is the resistance (R)? Show your work.
R = V/I
4V/5amps = .8 Ohms
If a circuit has a resistance measuring 7 ohms and a voltage of 3V, what is the current? Show your work.
I = V/R
3V/7R = .4 Amperes
Work and Power Practice. For POWER within a circuit. SHOW your work.
In physics, power is the rate of doing work (over time), and WORK is the determined by moving something with a
force over a distance. Energy is the ability TO DO work.
As you know, energy is measured in joules (J). Since power is a measure of energy over a set amount of time, we can
measure it in joules per second. The metric (SI) unit for joules per second in terms of ELECTRICAL Power is
the watt abbreviated as W.
Power, in terms of electrical power, is the amount of current times the voltage level at a given point measured in
wattage or watts OR the rate at which energy is transferred over time (which if you LOOK, it is still the same thing as
WORK over TIME because current x voltage at a set time IS the energy transferred over time).
P = V x I (Power = Voltage x Current)
1.
*Watts = Volts x Amps (per bulb).
A light bulb receives 6 amps of current and 9 volts from a battery. What is the Power Produced?
P = 9 volts x 6 amps
P = 54 watts
2. A battery gives off 12 volts with a current of 4 amps. How much power does each light bulb receive
in a series circuit if there are 3 light bulbs?
P = 12 volts x 4 amps
P = 48 watts
BUT there are 3 bulbs, so 48 watts ÷ 3 bulbs = 16 watts per bulb
All share the 48 watts of power, so 16 watts each! VERY dull lights due to sharing.
3. A battery gives off 9 volts with a
current of 12 amps. How much
power does each light bulb
receive in a parallel circuit if
there are 4 light bulbs?
P = 9 volts x 3 amps.
Each bulb =
27 watts. No sharing, so each bulb gets the 27 watts of power!
All nice and bright!