CASTLE Unit 2-READING 1€¦ · CASTLE Unit 2-READING 1 Schematic Diagram Figures Up to this point in our study of electricity, we have been representing our circuits by drawing “real

©Modeling Workshop Project 2004 1 C2 READ 1 v3.1

CASTLE Unit 2-READING 1 Schematic Diagram Figures

Up to this point in our study of electricity, we have been representing our circuits by drawing “real life pictures” of the circuit components. As we begin to study more complicated circuits it is necessary to introduce a simple, standard design for circuit components. These specialized symbols are recognized internationally by scientists and engineers. When using these specialized symbols, we call the circuit picture a schematic diagram, sometimes referred to as a circuit diagram.

When drawing schematic diagrams the convention is to replace cells, batteries, bulbs, etc… which may be made by different companies, have different covers (Energizer vs. Duracell) or shapes and sizes (like bulbs) with a single symbol for ANY cell, bulb, wire, etc…

What follows is a list of REAL PICTURES and their SCHEMATIC SYMBOLS which are to be used in schematic diagrams. Your job is to learn the proper symbols for each.

Consider the example of a complete circuit below.

Diagrammatic Symbols On the next page you will find a list of common circuit components and their schematic equivalent.

Real Picture

+ _

Schematic Diagram

R

R


Name Real Picture Symbol

Single cell

Battery (three cells) ** note – a battery is a combination of cells. You can make a battery with as many cells as you want – just keep adding single cells together!

Round Bulb (not lit)

Round Bulbs (Lit) ** Note – any kind of “rays” emanating from the bulb are good enough to indicate the bulb is lit

Long Bulbs (Not Lit)

Long Bulbs (Lit)

Capacitor

Compass (deflecting clockwise)

Compass (deflecting counterclockwise)

L

R

L

R

- +

+ -


What is a capacitor? Two layers of conducting material separated by a layer of an insulator form what is called a CAPACITOR. The name comes from the “capacity” of this three-layer device to store both charge and energy. The conducting layers are called PLATES. The insulating layer is sometimes referred to as a ‘dielectric’ layer. The insulating layer prevents movement of charge from one plate to the other inside the capacitor. You can make a simple capacitor by placing a sheet of waxed paper between two sheets of aluminum foil. In most capacitors the plates have very large surface area, so that they can store a large amount of charge. The plates are also made very thin, so that the three layers can be rolled into a cylinder and placed inside a small can. Each plate has a screw or a wire attached to it, called a TERMINAL, which extends outside the can and allows the plate to be connected to a circuit.

The “charge-holding” ability of a capacitor is called its CAPACITANCE. Capacitance is measured in a unit called the FARAD, named after the British scientist Sir Michael Faraday (1791-1867). The blue capacitor in your CASTLE kit has a capacitance of 0.025 farad, or 25,000 micro-farads, µF. (Some kits may also have a small silver capacitor, which will not be used at this time.)

Your teacher will have some large silver capacitors, which are to be shared by the class in a number of activities. These have a capacitance of 0.1 farad, or 100,000µF — four times as much as the blue capacitor.

NOTE: Sometimes capacitor plates may pick up stray charge that needs to be removed. A good way to avoid this problem is to keep a wire connected to the terminals of your capacitor when you are not using it. Also, after using a capacitor you will want to “reset” it so you can start all over again. To do this, touch a wire simultaneously to both of the capacitor terminals.

©Modeling Workshop Project 4 1 C2 ACT 1 v3.2

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CASTLE Unit 2 - Activity 1

New Terms:

Circuit A Circuit B

Connect circuit A. Carefully disconnect one wire and insert the battery as shown in circuit B. Call your instructor over to watch you connect Circuit B. To repeat the process, be sure and RESET the capacitor before completing Circuit A.

What is the effect of a capacitor on a closed loop?

Prediction(s): Observation(s):

Circuit Set-up Will the bulbs light?

Circuit A Yes / No

Circuit B Yes / No

On the back of this page, describe your explanations for both predictions. Use the terms and models that were developed in Unit 1. Underline the physics terms you use.

Circuit Set-up Did the bulbs light?

Circuit A Yes / No

Circuit B Yes / No

Consensus: Conclusion:


Name

Date Pd

CASTLE Unit 2 - Activity 2

New Terms:

Where does the mobile charge originate during the

charging and discharging process?

Circuit Will the bulb

light? R1 R2

charging Y / N Y / N

discharging Y / N Y / N

Circuit Point Compass Deflection?

A CW CCW NO

B CW CCW NO

C CW CCW NO

D CW CCW NO

E CW CCW NO

F CW CCW NO

G CW CCW NO

CW – Clockwise CCW – Counterclockwise NO – No Deflection

You should use the blue capacitor. You will use the compass to test the wires

labeled A – G shown in the schematic diagrams.

Remember to rotate the circuit while keeping the compass in one place!

Circuit

Did the bulb light?

R1 R2

charging Y / N Y / N

discharging Y / N Y / N

Circuit Point Compass Deflection?

A CW CCW NO

B CW CCW NO

C CW CCW NO

D CW CCW NO

E CW CCW NO

F CW CCW NO

G CW CCW NO

Use your observations to answer the focus

question!

Prediction(s) Observation(s)

Discharging

•

R 2

R 1

•

•

E

F

G

Charging

C

R 1

R 2

• •

•

A B

D

Conclusion: Conclusion:


Name

Date Pd

CASTLE Unit 2: Activity 3 How does a Genecon behave like a battery?

Procedure:

Turn the handle of the Genecon in a direction and speed so that the direction of charge flow and bulb brightness are the same as a 1-cell, 2-cell, and 3-cell battery. Count the number of turns of the handle that you make in 10 s for each trial. Repeat three times for 1-cell, for 2-cells and for 3-cells.

How does a Genecon behave like a battery?

Prediction(s): Observation(s):

Conclusion:

R

R R

R

How will the brightness of the bulbs in the 1-cell circuit compare to the 2-cell and 3-cell circuits? How will the compass deflection for the 1-cell circuit compare to the 2-cell and 3-cell circuits? How will the number of turns of the Genecon handle to match the bulb brightness in the 1-cell circuit compare to the number turns to match the 2-cell and 3-cell circuits?

Number of Cells

Bulb Brightness

Compass deflection.

1-cell

2-cell

3-cell

Number of Cells

Number of turns for each

trials

Avg

1st 2nd 3rd

1 cell

2 cell

3 cell

Consensus:

©Modeling Workshop Project 2004 1 C2 Read 2 v3.1

CASTLE Unit 2: Reading 2

Electrical Energy The term “energy” is probably one you often use. However, if you attempt to define it, you may find it difficult to do so.

“Energy” is the ability to make something happen. We have identified a number of things that happen in circuits – charges move, compasses deflect, bulbs heat and give off light. What is the source of the energy that makes these things happen? In most of the circuits we have observed, the source of the energy has been the battery. In some circuits, however, there was no battery present. When a capacitor discharges, it can make these same things happen, so it must also have been a source of energy, at least temporarily.

In some circuits, a Genecon was used, but the source of energy was the energy stored in your muscles. The cranking action transformed the energy from muscle storage to the energy of moving charges and bulbs releasing light.

You know that batteries eventually wear down, and may become “dead”. This means that they no longer have sufficient energy stored in them to make something happen in a circuit. Some batteries are called “rechargeable” and can be re-used. This is an incorrect term, however, since the batteries’ task was never to supply charge to the circuit – it was already there! These batteries would more properly called “re-energizeable”.

In the circuit, charge originates in every conductor, and constantly re-cycles around the circuit. However, energy leaves the energy source and travels one-way, leaving the circuit as heat thermal and light energy radiating from the bulbs (the receivers of the energy). The energy source might be the stored chemical energy in a battery, or the stored energy in muscles used to crank a Genecon, the stored electrical energy in a charged capacitor.


Stored Energy and Rechargeable Batteries A fresh battery (such as a single D-cell) generally contains two substances, which we will refer

to as A and B. These are high-energy substances (like some foods are known to be excellent sources of energy), which means that energy is stored in the chemical bonds within these substances. These two chemicals react inside the battery cell and release the energy that pushes charges around the circuit. The reaction is ‘rolling down’ the energy hill when energy is released from the cell. The equation for the reaction is: A + B → C + D + energy Eventually, however, substances A and B will be used up – completely converted into low-energy substances C and D. When only substances C + D are left, we refer to the battery as ‘dead’.

Some batteries, however, are designed so

that the chemical reaction is reversible. By pumping energy back into the system from another source, the chemical reaction can be forced in the opposite direction. The diagram on the right below demonstrates energy being absorbed into the battery, ‘climbing the energy hill’. The equation for the reaction is:

Energy + C + D → A + B

The battery is now ‘refreshed’ or ‘re-energized’ and can be used again to pump charges around a circuit. (The term ‘rechargeable’ is misleading, since a battery never runs out of charge. Charge is present everywhere in the circuit, and is not supplied by the battery. The battery simply supplies the energy needed to make the charge move through the circuit. The term “re-energizable battery” would be more accurate.)

©Modeling Workshop Project 2004 1 C2 WS 1 v3.1

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CASTLE Unit 2 - Worksheet 1 Capacitors and Charge Flow

Bulbs A and B light temporarily when the circuit in Figure 1 below is connected. 1. Will bulbs A and B light when connected as shown in figure 2? Explain your answer in detail. Using a battery, bulbs, wires, and a capacitor explain how: 2. to charge a capacitor 3. to discharge a capacitor 4. to find out if a capacitor is already charged without discharging it.

B A

Figure 1 Figure 2: Will A and B light?

A

B


Below are sketches of possible patterns of charge flow during the interval when the capacitor is charging, and when it is discharging. For each sketch, state whether or not the charge flow shown is correct (circle your answer). Support your answer by stating what is wrong with the charge flow arrows or what is correct about them. Use evidence to support your explanation.

5. Charging

R

R

R

R

+_

R

R

R

R

+_

+_

R

R

R

R

+_

R

R

R

R

6. Discharging

7. Charging 8. Discharging

A) Correct Incorrect B) Explanation:__________________ _______________________________ _______________________________ _______________________________





Name

Date Pd

CASTLE Unit 2: Activity 4 The Air Capacitor

Focus Question: How does an air capacitor operate?

Procedure: Perform the task described in the left column. Fill in each space provided in the

chart. Answer the focus question in your conclusion.

Procedure

Describe total amount of air in both chambers of the air capacitor

Describe movement of air in both chambers of the air capacitor

Near Chamber Far Chamber Near Chamber Far Chamber

While blowing into near end with the far end open

Increasing

Decreasing

Remaining Constant

Moving in

Moving out

No movement

While blowing into near end with the far end covered (closed) by your finger.

After blowing into near end with the far end open, closing the far end (w/ finger) then opening both ends

Section of drinking straw

Near End Far End

Near end

Far end

Conclusion: Consensus:


First sketch in the corresponding electrical circuit in the space provided. Then answer the following Focus Question by filling in the missing blanks in the chart below.

The Air Circuit Corresponding Electrical Circuit (Sketch the circuit in the space below.)

Focus Question: How is the air circuit analogous to an electrical circuit?

Air Circuit Electrical Circuit

The air pump causes air to move around the loop.

When charge stops moving, the positive(top) plate of the capacitor has an excess of charge.

After charging has stopped, the negative (bottom) plate has a deficiency of charge.

Pinching the tube so that it is completely closed off.

The air that enters the near chamber is not the same air that comes out of the far chamber.

The insulator between the plates.

The air in the tubes, chambers, and pump that is already present before any action is taken.

Near End Far End

Air moves this way



CASTLE Unit 2 - Reading 3

Benjamin Franklin’s “+” and “-” notation Movable charge is normally present in all conducting matter. Adding some charge to a normal capacitor plate will result in there being more than the normal amount of charge in the plate, while removing some charge will result in there being less than the normal amount of charge in the plate. Benjamin Franklin (1706-1790) came to the same conclusions when he did his pioneering work in electricity a few years before the American Revolution. Franklin is the person who first used (+) and (-) symbols in electricity. He used them to represent these two conditions: (+) represents a MORE-THAN-NORMAL amount of charge (“extra” charge) (-) represents a LESS-THAN-NORMAL amount of charge (“missing” charge) In the next section we shall begin using these symbols with the same meanings Franklin gave them. Franklin never knew about two kinds of charge. During the nineteenth century, the evidence for two kinds of charge became more compelling. Franklin’s symbols were retained but later given different meanings — as excesses of one kind of charge or the other. In this curriculum, the evidence for two kinds of charge will be presented in Section 8.


Name

Date Pd

CASTLE Unit 2 - Worksheet 2 Answer the following questions based on the air capacitor activity. Explain your reasoning in detail. 1. Does any of the air blown into one side of the capacitor come out the other? Explain. 2. How can you recognize a neutralized air capacitor? Explain. 3. For the air capacitor model, explain what happens when air is forced into one side of the

capacitor. 4. In the air capacitor model, explain what happens when air was drawn out of one side of the

capacitor. 5. What are the similarities between the purposes of the membrane and the air capacitor and the

insulating layer in the electric capacitor?


6. What are the physical differences between the insulator in the circuit capacitor and the

membrane in the air capacitor? 7. Sketch a qualitative graph that represents the amount of air in the near chamber vs. time during

the charging of the air capacitor. Sketch on the same set of axes a qualitative graph for the far chamber of the air capacitor. Use the following types of lines to represent each of the chamber volumes:

near: far :

Chamber Volume

normal volume

time

©Modeling Workshop Project 2004 1 12_C2 ACT 5.doc v3.2

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CASTLE Unit 2 - Activity 5 ….

What effect does the ‘size’ of a capacitor have on the amount of charge

and energy stored in the capacitor?

Prediction(s) Observation(s)

Variable Blue Capacitor

Bulb lighting time during charging.

Number of turn of the Genecon

handle during discharging

Variable Silver Capacitor

Bulb lighting time during charging.

Number of turn of the Genecon

handle during discharging

How will the bulb lighting time during charging of the blue capacitor compare to the bulb lighting time during charging of the silver capacitor? (greater than, less than or equal to) How will the number of turns of the genecon crank hand during discharging of the blue capacitor compare to the number of turns during discharging the silver capacitor?


R

R

Capacitor charging. Capacitor discharging.

You should perform multiple trials of both charging and discharging and record average values in the space below.

Documents

CASTLE Unit 2-READING 1€¦ · CASTLE Unit 2-READING 1 Schematic Diagram Figures Up to this point in our study of electricity, we have been representing our circuits by drawing “real