Ch20LevineE

Electric Circuits Investigation: Part 1
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Investigation 1:
What is needed to make a bulb light?

Hypothesis: In order to make a bulb light, a wire must be connected from the positive and negative ends of the battery to the metal clips on the lightbulb plate. No breaks in the circuit can be present.

Data: the positive and negative ends of the batter, and the clips attached to the light bulb. || || ON || clips attached to the bulbs. Only one wire connected to one end of the battery. || || OFF || positive and negative ends of the batter, but not connected to the clips attached to the bulb. || || OFF || attached to the wire, and connected to each other. No connection to the battery. || || OFF || attached to the bulb, and the other end of the wires both connected to the positive end of the battery. || || OFF ||
 * Setup || Picture || ON/OFF ||
 * Two wires connected to
 * Two wires connected to
 * Two wires connected to the
 * Two wires connected to the clips
 * Two wires connected to the clips

Analysis: Based on the image above, my hypothesis is correct. The bulb lit when a wire was connected to the positive and negative ends of the battery and to the metal clips on the bulb plate. A source of power and a closed conducting path ware necessary to light the bulb.

Investigation 2:
What happens to Bulbs 1 and 2 when you disconnect the wires of the configuration below at the various labeled points?



Hypothesis: If the wire is disconnected at any point, both the circuit will be broken and both bulbs will go out.

Data: Connected || || ON || At A || || OFF || At B || || OFF || At C || || OFF || At D || || OFF || At E || || OFF || At F || || OFF || Analysis: I found my hypothesis to be correct. If the wire is disconnected at any point the circuit will be broken and the lights will go out. There cannot be any breaks in a circuit, or else the flow of electricity will be disrupted.
 * Set Up || Picture || ON/OFF ||
 * All
 * Disconnected
 * Disconnected
 * Disconnected
 * Disconnected
 * Disconnected
 * Disconnected

Investigation 3:
What kind of object, when inserted into the spot labeled "something," in the loop shown below, will allow the bulbs to light?



Hypothesis: When a conductor is connected to the circuit the bulbs will light, and when an insulator is connected to the circuit the bulbs will not light. I think this based off of the definition of a conductor and insulator. A conductor is an object that allows for the free flow of electrons, and an insulator is an object that does not. If electrons can flow through a conductor, the circuit will not be interrupted and the bulbs should light.

Data: foil || || ON || ring || || ON || clip || || ON || Analysis: Based on my findings, my hypothesis was correct. Objects that are conductors will enable the light to turn on when they are attached to the circuit. The paper clip, aluminum foil, and metal ring are all conductors and caused the light to turn on. This is because they allow for the free flow of electrons, therefore not causing a break in the electric circuit. Objects that were insulators disabled the light from turning on when they were attached to the circuit. The string, the paper, and the cardboard are all insulators and did permit the light to turn on. Because they do not allow the free flow of electrons, these objects created a break in the circuit.
 * Object || Picture || ON/OFF ||
 * cardboard || [[image:cardboarddslfjk.png width="201" height="175"]] || OFF ||
 * aluminum
 * metal
 * paper
 * paper || [[image:papersldfj.png width="280" height="203"]] || OFF ||
 * string || [[image:string.png width="285" height="194"]] || OFF ||

Investigation 4:
What parts of a socket and bulb are conductors and which are insulators? What is the conducting path through the bulb?



Hypothesis: The clips, the plate, the threaded section, and tip will be conductors. I think this because they appear to be metal, and i know that metal is a conductor. Based on the preceding information,the base, the black ring, and the glass will be insulators.

Data: turned on when the circuit was connected to the tip of the bulb || Conductor || to the glass part of the bulb || Insulator || to the black ring of the bulb || Insulator || Section
 * Part || Picture/Observations || Conductor/Insulator ||
 * Base || [[image:touching_base.png width="215" height="184"]] || Insulator ||
 * Clip || [[image:touching_clip.png width="213" height="150"]] || Conductor ||
 * Plate || [[image:touching_plate.png width="209" height="151"]] || Conductor ||
 * Tip || unable to take picture, but the light
 * Glass || unable to take picture, but the light turned off when the circuit was connected
 * Black Ring || unable to take picture, but the light turned off when the circuit was connected
 * Threaded

Filament || unable to take picture, but the light turned on when the circuit was connected to the threaded section of the bulb

|| Conductor

Conductor || Analysis: My hypothesis was correct. All the elements made of metal were conductors. The light turned on when the circuit was connected to the threaded section, the tip, the plate, and the clip. This indicates that they are conductors because they allowed for the free flow of electrons, which allowed the circuit to flow continually, and allowed the bulbs to light. The black ring, glass, and base are insulators, because they did not allow the bulb to light when connected to the circuit.The conducting path through the bulb starts at the metal tip, goes through the threaded metal section, and into the filament to light the bulb.

Investigation 5:
How can you light a bulb using one battery, one bulb, and one wire ONLY? How many different correct ways can you do this? What didn't work and why?

Hypothesis: In order to light a bulb, one wire must be connected to the positive and negative ends of a battery, and this wire must also be connected to a conducting part of the bulb. I think this because connection to a positive and negative terminal are needed to set up a circuit. The wire must be connected to a conducting part of the bulb so that electrons can flow freely to the bulb.

Data: negative ends of the battery. The bulb is not touching the wire, but is touching one end of the battery. || || No || negative ends of the battery. The wire is not touching a conducting part of the bulb. || || No || negative ends of the battery. The wire is also connected to the conducting tip of the bulb. || || Yes || negative ends of the battery. The wire is also connected to the conducted coiled section of the bulb. || || Yes || opposite ends of the battery. || || Yes || attached to opposite ends of the battery. || || Yes || Analysis: My hypothesis is correct based on the data collected throughout the experiment. In order to light a bulb with just one bulb, one wire, and one batter, certain conditions have to be met. Firstly, the wire needs to touch both the positive and negative ends of the battery. Secondly, a conducting part of the bulb needs to be connected to one end of the wire. There are four ways to make the bulb light up. One way is to hold the wire to the positive and negative ends of the battery, and to hold the threaded conducting part of the bulb up to one end of the wire. Another way is to also hold the wire to the positive and negative ends of the battery, but to hold the conducting tip of the bulb up to one end of the wire. These two methods can be replicated on either terminal of the battery, producing four different methods of lighting the bulb in this scenario. Trials did not work when I did not connect the wire to a conducting part of the bulb. This is because the free flowing path of electrons was broken.
 * Setup || Picture || Yes/No ||
 * 1. A wire connected to the positive and
 * 2. A wire is touching the positive and
 * 3. A wire connected to the positive and
 * 4. The wire is connected to the positive and
 * 5. Same setup as 3, but wires are attached to
 * 6. Same setup as number 4, but the wires are

Investigation 6:
What does a compass tell you about what is happening in the wires of the circuit?

Hypothesis: When the electric current is run over the compass, the needle will be deflected away from its original Northern direction.

Data:

media type="file" key="video1.mov" width="300" height="300" Analysis: The compass needled moved when the wire was connected to the battery. The needle is affected by the wire only when both ends of the wire are connected to the battery. At this time, a current of electrons are running through the wire and deflect the needle of the compass.

Investigation 7:
What effect does reversing the battery pack have on the compass deflection? What does it tell you about the role of a battery pack in the circuit?

Hypothesis: I think the compass needle will be deflected in the opposite direction of investigation 6. This is because the charges are moving in the opposite direction.

Data: media type="file" key="video2.mov" width="300" height="300"

Analysis: My hypothesis was correct, the needle was deflected in the opposite direction that it was in investigation 6. This is because the needle is deflected based on the flow of charges. When the battery pack was reversed, the charges were moving in the opposite direction, so the needle was deflected in the opposite direction too. The battery pack in the circuit pushes the charges through the circuit in one direction or another.

Investigation 8:
What is a Genecon and how does it work? What does it tell you about the role of a battery in an electric circuit and why?

Hypothesis: The Genecon will act similarly to a battery, pumping the electrons through the circuit.

Data: media type="file" key="Movie on 2011-10-14 at 14.15.mov" width="300" height="300"

Analysis: My hypothesis was correct. The Genecon pumped the electrons through the circuit to light the bulb the same way a battery does. An internal motor converts the mechanical energy of spinning the handle into electrical potential energy. This EPE pushes the electrons through the circuit, the same way a battery would. Based off of my observations, I realized that batteries don't provide electrons to pump through the circuit, they merely provided an electric potential difference that pumps electrons through the circuit.

Investigation 9:
What is the effect of a capacitor on a closed loop?

Hypothesis: A capacitor will stop the flow of electrons in a closed loop, and cause the bulbs to go out. This will happen because of the insulating material inside of a capacitor.

Data: media type="file" key="Movie on 2011-10-14 at 14.41.mov" width="300" height="300"

Analysis: My hypothesis was correct, except not entirely complete. The batteries push protons through the circuit, and the protons accumulate on one side of the capacitor because they cannot cross the insulating barrier. This causes a repulsion to be felt by the protons on the other side of the insulating material, so they flow to the other end of the battery. During this time, charges are flowing and the battery is lit. However, when no more protons can accumulate on one side of the capacitor, the flow of charges stops and the bulbs will go out. This is why the video shows the bulb lighting for a second or two, and then immediately going out. In real life, capacitors are used to power machines when they are turned off. For example, a capacitor will run the clock in the car, even when the car is not turned on.

Investigation 10:
What is the origin of mobile charge? From where does the mobile charge originate during the charging and discharging process?

Hypothesis: The mobile charge will originate from the protons in the circuit during charging, and from the accumulation of protons on one side of the capacitor during discharging.

Data: media type="file" key="Movie on 2011-10-14 at 14.50

Analysis: Based on the data above, I conclude that my hypothesis was correct. During the charging process, the mobile charges originate from the entire circuit. The positive charges are pushed by the battery to the capacitor and stopped by the insulating material. The charges accumulate at one end of the capacitor and cause an electric field, in which the like charges on the other side are repelled and pushed towards the other end of the battery. During the discharging process, the mobile charges originate from the accumulation of protons at one end of the capacitor. The positives move back to their original positions in the circuit.

Questions
__Question A:__ What is a conductor and what is an insulator? How do you know? How can you test this using our loop configuration?

A conductor is an object that electrons can move through freely. In a conductor, the outer electrons of the atom are loosely bound and free to move through the material. Most metals are known the be conductors. On the contrary, an insulator is an object that electrons cannot more through freely. These atoms hold onto their electrons tightly, and do not permit a fluid movement. Most non-metals are known to be conductors. Using the loop configuration depicted above, it is easy to test if an object is a conductor or an insulator by connecting the object to the circuit. If the bulb lights, we can conclude that the object placed in the circuit is a conductor. This is because the electrons were able to flow freely through the object, delivering the flow of electrons to the bulb. If the bulb does not light, we can assume the object placed in the circuit is an insulator. This is because the object cannot allow for the free flow of electrons, and creates a break in the circuit.

__Question B:__ What is a circuit?

A circuit is a complete loop in which charges can flow through freely. The loop must be made up of conducting materials so the charges can travel around the circuit. A circuit must have a source of electric potential difference to push the charges, and closed wires that can carry the charges throughout the loop.

__Question C:__ What is a schematic diagram? What are the symbols for the various circuit elements?

A schematic design is a universally known method of drawing circuits. Instead of drawing what the objects actually look like, different symbols are used to represent different parts of the circuit. The symbols are as follows below.

(Deflecting Counterclockwise) || ||
 * Object || Symbol ||
 * Single Cell || [[image:single_cell.png]] ||
 * Battery Three Cells || [[image:battery.png]] ||
 * Round Bulb (Not Lit) || [[image:Round_Bulb_Not_Lit.png]] ||
 * Round Bulb (Lit) || [[image:round_bulb_lit.png]] ||
 * Capacitor || [[image:capacitor.png width="78" height="56"]] ||
 * Compass (Deflecting Clockwise) || [[image:compas_clockwise.png]] ||
 * Compass
 * Connecting Wire || [[image:connecting_wire.png]] ||
 * Resistor || [[image:resistor.png]] ||

__Question D:__ What is a capacitor and how is it made?

A capacitor is an object that can store electrical energy when it is connected to a power source. A capacitor is made of two layers of conducting material, with a layer of insulating material in the middle. These layers are rolled up into a cylindrical shape, and have a positive and negative terminal. When the capacitor is connected to a circuit, the charges from the positive end of the battery accumulate on one end of the insulating material. This creates an electric field, and the charges on the other side of the insulating material are repelled to the negative end of the battery. While still connected to the battery, the bulbs in the circuit will flash and then go out. The amount of time they flash for is determined by the capacity of the capacitor, or the room it has to accommodate the accumulation of positive charges. This temporary charge is used frequently in the real world. For example, capacitors are used to run the time in a car, even when the car is turned off.

Practice Sets
__1. The CCP__





__2. Basic Circuits__


 * I CHANGE MY ANSWER IN NUMBER ONE TO D (THEY ALL LIGHT AT THE SAME TIME). THIS IS BECAUSE THE CHARGES ORIGINATE FROM THROUGHOUT THE CIRCUIT, NOT THE POSITIVE TERMINAL OF THE BATTERY.


 * I CHANGE MY ANSWER IN THE FIRST DIAGRAM TO BULB 1 WILL LIGHT, and BULB 2 WILL NOT LIGHT. BULB 1 WILL LIGHT BECAUSE IT IS CONNECTED AT BOTH THE TIP AND SIDE.


 * __3. Wires__**

C

Both bulbs will light with the same brightness. The paper clip is a conductor, which allows for the free flow of charges. Regardless of where the paper clip is placed, the bulb will be equally bright. If an insulator, which doesn't allow for the free flow of charges, was placed in one of the circuits, the bulb would go out.
 * 2. Explain why you believe your answer to Question 1 to be correct. Use the words "insulator" and "conductor" correctly as part of your explanation.**

A circuit includes a source of electric potential difference to pump charges, a closed path for charges to flow through, and a unit for the charges to be "used" (ex. a bulb). A circuit must be a closed loop, with no breaks.
 * 3. Write in your own words a definition of the word __circuit__ which anyone could use do determine if a given set of connections is or is not a circuit.**

Air is an insulator in most cases, because electric charges cannot be moved through it. However, in cases of high voltage like lightning, air can act as a conductor.
 * 4. We have observed in several activities that as soon as a very small gap is produced anywhere in the circuit, the bulbs go out. Would you classify air as a conductor or an insulator?**
 * Explain.**


 * 5. Indicate whether each of the following statements is True or False. Then state evidence which either supports or contradicts each statment.**

False. Positive charges leave the positive terminal of a battery, and ENTER the negative end of a battery. This cyclic movement is what creates electricity. This was also proved in the experiments we did with the compass. When we reversed the battery, the compass deflected in opposite directions, indicating that charge only flows out of one end of the battery. True. No matter which way a light bulb is connected to a circuit, it will behave the same way. This is because of the continuous conducting path that can run either way in a bulb. In my experimenting, I found that it does not matter which way the wires are connected, the bulb will still light. True. The battery creates the electric potential difference which pushes the charges through the circuit. Naturally, the charges move from positive to negative. The battery makes the charges travel out of the positive terminal and into the negative terminal. In the compass experiment, reversing the battery resulting in the compass deflecting in the opposite direction as it previously had. This proves that the battery determines the direction of charge flow. False. Based on my experiments, a compass will show deflection when charges are running, and will deflect in the opposite direction when the battery is reversed. However, since we don't know the original direction of the charge, it is impossible to determine which deflection means which direction. True. Metals have loosely bound valence electrons, which makes them free to move throughout the object. Also, in experimenting all metal substances that were connected to a circuit lit the bulbs and allowed for the free flow of charges.
 * A. Charge moves out of each end of the battery into the loop.**
 * B. Light bulbs are non-directional devices. (Whichever way they are connected in the circuit, they behavie the same way if you turn them around)**
 * C. The battery determines the direction of flow of charge in a circuit.**
 * D. A compass can be used to determine the exact direction that charge flows in a circuit.**
 * E. Metal substances are generally conductors.**


 * __4. Schematics__**



Bulb A will go out, because it will no longer be connected to the circuit on both ends. The conducting materials in bulb B will not provide a continuous path for the charges to flow through, unlike when it is connected.
 * 2. Describe what, if anything, will happen to bulb A if bulb B is removed from its socket. Explain your reasoning.**

A conductor is an object that allows for the free flow of electrons. An insulator is an object that does not allow for the free flow of electrons.**
 * 3. According to the work done in this unit, what is a conductor? an insulator?**







__5. Electrical Energy__







__6. Investigating the Air Capacitor__











__7. Capacitance__







Reading Questions
__1. Schematic Diagrams__

__2. Capitance__





#1
What effect does the type of bulb have on a capacitor during charging and discharging?

Hypothesis: The time to discharge the capacitor will change with each method of discharging, due to various levels of resistance.

Data:

Discharging Through Round Bulbs media type="file" key="discharging through round bulbs.mov" width="300" height="300"

Discharging Through Long Bulbs media type="file" key="discharging through long bulbs.mov" width="300" height="300"

Discharging Through Genecon media type="file" key="discharging through genecon.mov" width="300" height="300"

Analysis: My hypothesis was correct. The discharging process through the genecon and the round bulb took longer than the discharging process through the long bulbs. This was shown because the bulb took longer to go out during discharging with the long bulb, than the round bulb. Also, the handle of the genecon spun for a longer amount of time than the round bulb took to go out. This leads me to believe that the long bulb has more resistance than the genecon and the round bulb.

#2
What are the differences between the filaments of round and long bulbs? (use a microscope)

Hypothesis: I believe that one one filament will be thicker than the other, creating a difference in resistance between the two bulbs.

Data:
 * Bulb || Observations ||
 * Round || thicker and shorter ||
 * Long || thinner and longer ||

Analysis: My hypothesis was correct, but also incomplete. The round bulb has a thicker filament, and the long bulb has a thinner filament. This explains why only the long bulb will light when attached to a circuit with a round bulb in it also. Because the round bulb has a thicker filament, it has less resistance. Therefore, it takes more current to make the bulb light. On the contrary, the long bulb has a thinner filament, and it will light with less current.

#3
How is air moving through straws analogous to charge moving through a filament?

Air moving through a straw is an accurate depiction of charge moving through filaments in a circuit. It was easier to blow air through the soda straw than the coffee straw. This is because the soda straw has more room for the charges to flow, and less resistance. Similarly, charge will move more easily through a thicker filament, because thicker filaments have low resistance to charge flow. This indicates that the filament of a round bulb has little resistance. The coffee straw is analogous to the filament in the long bulb. They both have a thinner path, creating more resistance to air and current. Additionally, the longer the filament, the more resistance it has to current. This was shown when we tried to blow through two straws, and it was more difficult than trying to blow through one straw.

#4
What is the difference between flow rate and flow speed?

Flow rate and flow speed are often confused, but it is important to realize the distinction between them. Flow rate is the amount of charge, or number of charges that pass a certain point in a circuit during a set interval of time. Flow speed is the velocity at which the charges move throughout the circuit.

#5
How does the number of bulbs in a single loop affect the overall current and resistance in a circuit? Hypothesis: The number of bulbs will not affect the overall current and resistance.

Data:

1 bulb media type="file" key="1 bulb.mov" width="300" height="300"

2 bulbs media type="file" key="2 bulbs.mov" width="300" height="300"

4 bulbs media type="file" key="4 bulbs.mov" width="300" height="300"

Analysis: My hypothesis was correct. The number of bulbs in a series circuit did not affect the overall resistance or current. I can infer this because the compass needle deflected approximately the same amount when held up to a circuit with one, two, and four bulbs. Had the current/resistance been affected, the amount of deflection shown by the compass would have changed. All the round bulbs have the same resistance, therefore the flow rate remains the same even when more bulbs are added.

#6
Problem Set: Resistance







#7
Read Lesson 3

#8
Reading/Questions- Pressure Difference

1. Write a sentence summarizing the points of the first argument. use your own words. Like water, charges cannot compress themselves to fit more charges in a designated area.

2. Write a sentence summarizing the points of the second argument. Use your own words. Like air, charges can compress themselves to fit more charges in a designated area. Charges also move from high to low pressure.

3. Based on your understanding of the reading, which argument is the closest fit to the behavior observed in actual circuits? The second argument

4. In terms of electric pressure, how does charge "know" which direction to move? From high pressure to low pressure

5. During the charging process there comes a time when the bulbs no longer light. Does this mean that the battery has stopped pumping charge? Explain your thinking. No, it just means there isn't enough of a pressure difference for the charges to run through the circuit.

6. What is the technical term for Electric Pressure? Electric Potential

7. How does a charge "know" when to stop moving? How does this explain the inability of a "dead" battery to play a portable CD player? When there is no electric pressure difference charges stop moving. In a "dead" battery the electric pressure across the wires is equal, so there is no flow. This makes it impossible for the portable CD player to work.

#9
Notes/Activity-Color Coding











#10
Practice Set-Color Coding









#11
How does the number of bulbs side-by-side affect the overall current and resistance in a circuit? Hypothesis: Adding bulbs in parallel will not affect the current or resistance in a circuit.

Data: Deflection || Bulb Brightness ||
 * Bulbs || Compass
 * 1 || same || same ||
 * 2 || same || same ||
 * 3 || same || same ||

Analysis: The number of bulbs parallel to each other in a circuit does not change the overall current/resistance. In each of the diagrams above, the compass deflected the same amount, indicating that the current and resistance remained constant. This is because the wires are ALL connected to the battery. Therefore, the bulbs experience a blue-to-red pressure difference in ALL parallel setups, and light with equal brightness.

#12
Does adding wires in a series or in a parallel affect the overall resistance of the circuit? Hypothesis: Wires have no resistance so they will have no effect on the overall resistance of a circuit.

Data: Deflection || Bulb Brightness ||
 * Circuit || Compass
 * A || small deflection || bright ||
 * B || same as A || same as A ||
 * C || more deflection || short circuited bulb goes out, and other bulb gets brighter ||

Analysis: Adding wires in a series circuit has no effect on the resistance of the circuit. This is because wires have no resistance, and therefore do not change the current passing through the circuit. I can infer this because the compass deflected the same amount with an additional wire in the circuit, than it did without it. However, adding another wire in a parallel circuit does affect the overall resistance of the circuit. The wires form a junction and the charges moving through the wires must choose one path to go down. Now, there are half as many charges moving through each wire as before, and the speed of the charges increases. This means there is less resistance, and the bulbs will light more brightly.

#13
What effect do dueling battery packs have on bulb lighting and flow rate? Hypothesis: Dueling battery packs will increase bulb lighting/flow rate when placed in the same direction, and decrease lighting/flow rate when placed in the opposite direction of the original batteries.

Data:
 * Circuit || Results ||
 * A || bulbs light brightly ||
 * B || bulbs light a little less brightly ||
 * C || bulbs light a lot less brightly ||
 * D || bulbs light brighter ||

Analysis: Dueling battery packs can have multiple effects on bulb lighting and flow rate based on the direction they are inserted. If the battery packs are inserted in opposite directions, the batteries will act as resistance. Therefore, the bulbs will not be as bright, and flow rate will decrease. For example, if a circuit has 3 batteries attached in one direction, and one battery attached in the opposing direction, it is equivalent to having the net "push" of two batteries. This is because the opposing batteries act as resistance and push the charges in the opposite direction of original charge flow. However, if battery packs are inserted in the same direction, the bulbs will be brighter and the flow rate will increase. The addition of batteries in the same direction merely add more electric potential difference to push the charges. For example, if a circuit has 3 batteries attached in one direction, and 3 more batteries attached in the same direction, this is the same as having a net "push" of six batteries.

#14
Practice Set-Battery Structure



#15
How does mixing bulbs in a series affect flow rate and pressure in each part of a circuit? Hypothesis: I think that only the long bulb will light because it has more resistance than the round bulb. However, when the long bulb is short circuited, it will go out and the round bulb will light.

Analysis: My hypothesis was correct, when a long and round bulb were in series, only the long bulb lit. This is because the flow rate is constant in the circuit, and it adjusts to the most resistant object (the long bulb). As a result, there wasn't enough current to light the round bulb, even though current was flowing through it. When the long bulb was short circuited, it went out because the charges took the path of least resistance. The round bulb lit because now the current increased to match the resistance of the round bulb, and enough charges passed through to light it.

#16
Reading-Mixing Bulbs







#17
What is the effect of adding another round bulb in parallel? Set up the 3-bulb circuit in the figure on the left, with a gap for a 4th bulb to be added. Then add the 4th bulb to form the circuit in the figure on the right. Two switch back and forth between the two circuits, you can add the 4th bulb and its socket, and simply unscrew the 4th bulb to break the connection.

Hypothesis: I think that adding another bulb in parallel will increase the flow and make the bulbs brighter.

Analysis: My hypothesis was wrong. When another round bulb was added in parallel, the two bulbs in parallel went out, indicating that flow decreased. However, the two bulbs on the side became brighter, showing that flow increased in that series circuit. This can be explained by the fact that the addition of an extra bulb in parallel gives the charges two paths two choose from. Half as many charges are passing through the two middle bulbs, causing the bulbs to dim. However, the same amount of charges are still running through the two bulbs in series, causing them to brighten.

#18
How does the addition of another branch affect flow rate and pressure in the wires? Assemble a circuit with a 3-cell battery and a round and long bulb in series. Using a compass, measure the flow rate in wires A and B. Add a branch with a second long bulb parallel to the long bulb, but don't make the connection. Predict what will happen to the bulb brightness and flow rate when the connection is made. Repeat for a round bulb and for a connecting wire.



Hypothesis: I think that flow rate and pressure will increase when the long and round bulbs are added. The wire added will have no effect because wires have no resistance.

Data: Circuit 1: All bulbs light Circuit 2: Round bulbs light and the long bulb dims Circuit 3: Round bulb lights and long bulb goes out.

Analysis: The effect that the addition of another branch in parallel has on the circuit is dependent upon the resistance of the added branch. Adding another long bulb in parallel increases the flow which can be seen by the fact that the round bulb becomes a little brighter. Before, it could not light because of the resistance of the long bulb it was in series with, but now the addition of the long bulb in parallel increased the flow rate and allowed the round bulb to light. The addition of the round bulb in parallel causes the flow rate to increase even more, because it has less resistance, but causes no change in pressure. In the third circuit, a wire is added in parallel to the long bulb. This forms a short circuit, and causes the long bulb to go out and the round bulb to light. The round bulb can now light because the circuit has less resistance due to the elimination of the long bulb from being short-circuited. The pressure in the wires in this circuit increases.

#19
What is the effect of decreasing the resistance on the right side of the circuit on: a. the flow rate through the battery b. the pressure difference across the battery c. the brightness of the left bulb



Hypothesis: I think that flow rate will increase, the pressure difference will stay the same, and no effect on the brightness of the bulbs.

Data: Circuit A: bulbs light and compass deflects Circuit B: left bulb dims, compass is deflected more towards A Circuit C: left bulb dims, compass is deflected more than in circuit B

Analysis: When the resistance on the right side of the bulb was decreased, the flow rate increased. In circuit B the flow rate increased, and in circuit C the flow rate increased even more. I was able to tell this because of the compass deflection. In circuit B, the compass deflected more than it did in circuit A, and in circuit C, the compass deflected more than it did in circuit B. The pressure in the circuit is not effected, because none of the bulbs become brighter or dimmer. If the pressure increased, the bulbs would become lighter, and if the pressure decreased the bulbs would become dimmer.

#20
Practice Set- What Determines Pressure in the Wires?



#21
Activity: Ammeter Voltmeter











#22
T/F

Homework Summary-10/10
1. I understand the demonstration about electric potential difference and charge flow. The electrons run from the positive charge to the negative charge, until there are barely any left. Slowly, their electric potential differences become equal, and there is no more charge flow. For an electric circuit to exist, charges must continually flow through a complete loop. An energy supply and a closed conducting pathway are needed to create a conducting circuit.

I understand that electric current is the rate of the flow of electrons past a certain point in a circuit. This rate is measured in amperes, a.k.a. amps. The direction of an electric current is by convention in the direction that a positive charge would move. It runs towards the negative terminal, away from the positive terminal.

2. I am a little confused about the difference between current and drift speed. What exactly is the difference between them? Is it that drift speed is more of an average speed, and current is instantaneous?

3. There wasn't anything I didn't understand. The Physics Classroom did a good job of explaining all material.

Lab: Ohm's Law
Purpose: What is the relationship between pressure difference and flow rate? What is the difference between Ohmic and Non-Ohmic materials?

Hypothesis: I believe that pressure difference and flow rate have a linear relationship, based on Ohm's Law, which states that voltage is equal to the current times the resistance. Also, Ohmic materials will follow this linear relationship, and Non-Ohmic materials will not.

Procedure: Measure Voltage and Current in circuits with different resistors using the following setup:



Data:



Sample Calculations:

R=V/I R=11/.05 R=220 Ohms



Graphs:

The data on the graph shows the relationship between potential difference and current. The two linear graphs are Ohmic, because they follow the relationship of V=IR. The slope of these graphs represent the resistance of the materials. The two non-linear graphs are Non-Ohmic, because they do not follow the relationship of V=IR.

3. In both instances, the lines to represent these relationships would be straight horizontal lines. This is because the resistance stays constant.

Conclusion: My hypothesis was correct. The data shows that pressure difference and current have a linear relationship for Ohmic materials. As voltage increases, so does the current, based off of the Ohm's Law equation V=IR. The slope of these linear equations represents the resistance of an object. My data was fairly correct, with a percent error of 13.8%. A resistor that was known to have a resistance of 220 Ohms, had a slope of 193.3, fairly close to the actual resistance. However, this doesn't represent an exact percept error, because it doesn't take into account the percent error of the resistor. Therefore, it is likely that my percent error is even less than 13.8%. I was also correct in hypothesizing that Non-Ohmic materials would not follow a linear relationship. The two bulbs are Non-Ohmic and did not show a linear relationship. My error was fairly low for the two resistors, but high for the two bulbs. Error on the bulbs reached as high as 89%. I believe this might have been because we estimated the resistance of the bulbs, we did not know for sure. Another source of error in this experiment was the accuracy of the measuring device. These values may have been off a little, therefore adding error to my experiment. In the future, I think its important to find the precise resistance of the two bulbs, in order to get more accurate results. Also, if we could use a more accurate device, this might produce more accurate results.

Lab: Kirchoff's Rules
Purpose: Determine how current splits in multi-loop circuits.

Hypothesis: When the current splits in a circuit, it divides between the two paths at the junction. Therefore, less charges are flowing through each wire, and the flow rate will increase because there will be less traffic in the wires.

Procedure: 1. Draw an image/schematic diagram of the circuit 2. Use an Ammeter/Voltmeter to measure the current and voltage at each resistor 3. Perform calculations to see if theoretical values match experimental values 4. Repeat for all 4 circuits.

Data: Circuit A


 * Resistance(Ohms) || Voltage(V) || Current(A) ||
 * 300 || 2.78 || 15.6 ||
 * 300 || 1.57 || 10.21 ||
 * 560 || 2.16 || 10.21 ||
 * 100 || 2.32 || 22.45 ||
 * 100 || 1.54 || 7.82 ||

Circuit B


 * Resistance(Ohms) || Voltage(V) || Current(A) ||
 * 500 || 3.84 || 7.4 ||
 * 750 || 5.69 || 2.58 ||
 * 1000 || 1.57 || 7.89 ||

Circuit C




 * Resistance(Ohms) || Voltage(V) || Current(A) ||
 * 1000 || 9.32 || 9.5 ||
 * 820 || .48 || .6 ||
 * 680 || 5.53 || 8.0 ||
 * 580 || .52 || 1.22 ||

Circuit D


 * Resistance(Ohms) || Voltage(V) || Current(A) ||
 * 100 || 4.13 || 40.01 ||
 * 200 || 1.62 || 6.82 ||
 * 475 || 1.4 || 38.7 ||

Sample Calculations:

Circuit A

Circuit B

Circuit C

Circuit D

Analysis:

Sample: Percent Error for Voltage R1 Circuit A

Discussion Questions:

1. Are the experimental values of the currents for the entire lab generally larger or smaller than the theoretical values expected for the currents? 2. It was pointed out in the lab that some error might be caused by neglect of the internal resistance of the //emf.// Would the internal resistance cause an error in the direction shown in your answer to question 1? State your reasoning for the direction of any error caused by internal resistance. 3. An ideal ammeter has zero resistance. Real ammeters have small and finite resistance. Would ammeter resistance cause an error in the proper direction to account for the direction of your error indicated in question 1? State your reasoning. 4. The connecting wires in the experiment were assumed to have no resistance, but in fact have a finite resistance. Would this error in the proper direction account for the direction of the error stated in your answer to question 1? State your reasoning. 5. What is the meaning of any current values obtained in your solutions that are negative?
 * My experimental values were generally larger than my theoretical values.**
 * No, internal resistance would lower the experimental values of the current through the wires, not increase it. According to Ohm's Law, V=IR. If voltage was constant and resistance increased, current would decrease.**
 * No, resistance added from the ammeter would lower the experimental values of the current through the wires, not increase it. According to Ohm's Law, V=IR. If voltage was constant and resistance increased, current would decrease.**
 * No, once again additional resistance from the wire would cause the experimental values of current to decrease.**
 * There is no significance of a negative solution, it should just be turned into a positive solution. All that it means is that the current is moving in the opposite direction of the way I set it up in the beginning of the problem.**

Conclusion: My hypothesis was correct. When charges split at a junction, the flow rate increased because of less traffic in the wires, and the amount of current in the first wire would equal the amount of current in the second two wires. For example, in circuit A, I1 was equal to 22.45, and I2+I3 was equal to 20.41. These values were relatively close and prove my thinking to be correct. The accuracy of my values ranged, as I had percent errors from .25% to 48.9%. I attribute the large range of percent error to many sources of error in this experiment. Firstly, the method of collecting data was very flawed. When we used the ammeter/voltmeter, it was very hard to tell if we were getting accurate results. The numbers would constantly fluctuate, based on the amount of pressure applied. It was impossible to apply constant pressure throughout the entire experiment, so it is likely that our results are flawed as a result. Also, we ignored the batteries' internal resistance, the resistance of the wires, and the resistance of the measuring devices. Had we taken these values into account, we would have gotten more accurate results. For the future, this experiment would run more smoothly with a more accurate device to measure current and voltage. I believe the inaccuracy of the devices we used contributed the most amount of error to my results. Additionally, we should take into account the resistance that is present due to other factors that only the resistors.