Path Finders

 

 

3.0 It's All in The Connections

Use these three things pictured below.to light the bulb.

Draw six working arrangements of the battery bulb and wire.

3.11 Simple minimum requirements for a working electric circuit are as follows:(Label #1, 2, 3 on your drawings)

.11 a source of electric energy

.12 a complete conducting path.

(Draw in what you think the wire connections are is inside the base.)

.13 an appliance (electric energy converter)

 

3.20 Two Useful Path Connections:

.21 single path , Series circuit

A good simple example of a single path (series) circuit is a string of dependent Christmas tree lights.

What happens when one light blows out or is removed?

_____________________lights go out.

(All / Only the defective )

Explain how you decided the correct choice for the question you just answered.

__________________________________________________________________________________________________________________

Draw the hidden (socket /bulb-wire) connections for the circuit.

.22 multiple path , Parallel circuit

A good simple example of a multiple path (parallel) circuit is a string independent Christmas tree lights.

What happens when one light blows out or is removed?

____________________________________________________.

Explain how you decided on the correct choice for the question you just answered.

_____________________________________________________

Draw the hidden (socket /bulb-wire) connections .

Circle the following diagram which best describes the parallel connection

.23 Mystery Paths:

Circuits are often hidden. Their paths may be traced by inference, opinion supported by observation. Often these opinions must be changed after further testing.

Use this circuit tester to develop an opinion about the path of the hidden circuit between the lettered foil test points.

If the bulb lights you may infer the two foil circles are connected.

On the "Observation Sheet" provided draw in a wire between the circles which light the bulb

 

.23A Tracing mystery Paths

"Observation Sheet"

Now simplify your infered connections using only three wires.

Can you draw four possible connection patterns which agree with your observations.

Making the inference board.

Possible infered wire connections whose observations would agree

 

 

.23B Tracing Mystery Paths In the Real World

You will be given switches used in real life situations. As on the mystery board their internal connections are hidden.

[1] Use your circuit tester and operate the switches.

Test all the combinations of contacts with all positions of the switch.

[2] Draw and label the hidden switch circuit.

[3] Design a circuit which would take advantage of the design features of each switch.

3.30 Series, Single path (simple unbranched circuits)

(Series means one path )

Fact: The brightness of the light bulb indicates the current flow

.31 How does adding batteries affect the current strength?

Materials for connection

Circle the light which best shows the bulb brightness

 

 

 

 

.31 Adding batteries ______ (weakens/strengthens) the current if there is only a single path in the circuit

.32 How does increasing the lamps affect the current?

Materials for connection

Draw In the wires to light the bulb

 

Increasing the Number of lamps

 

Conclusion:

Increasing the number of lamps connected in a single path _________ the current. (increases/decreases)

 

Materials for connection

Draw In the wires to light the bulb

Increasing the Number of lamps

 

 

.32 Adding lamps ________ (weakens/strengthens) the current if there is only a single path in the circuit

.33 How does removing one part of the circuit affect the rest?

(Use the following single path or series, circuit to find the answer)

Circuit for Investigation

 

Remove a bulb.

Replace it

Try the others

Replace it

Try each wire

Replace them

.33 One bulb removed causes ________the bulbs to go out. (one / all)

.34 Usefulness and Application

Question 1:

How could you find the faulty bulb if you had a string of these bulbs.

( as in a single path Christmas tree set)?

Answer:

________________________________________________________________________________________________________

Question 2:

.How could you find the fault with a lamp that doesn't work?

(The lamp has a touch control switch, a heat sensing fuse, and a bulb all in series.)

Answer:

________________________________________________________________________________________________________________

Question 3 (Diagrams):

 

Notice how fuses are connected in the following diagrams:

.35A Cryptogram

Cryptogram Key

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o pq r s t u v w x y z

n o p q r s t u v w x y z

Text:

If you find the fault is with the

fuse it cut the circuit to protect

you.Notice how fuses are connected in

series. All the electric current for the protected

circuit goes through the fuse.

When it blows the circuit is turned

off. To either replace the fuse with one of higher value or

wire around it with a coin is to defeat a safety

device designed to

protect you.

Answer:.35A Cryptogram

If you find the fault is with the

fuse it cut the circuit to protect

you. Notice how fuses are connected in

series. All the electric current for the protected

circuit goes through the fuse.

When it blows the circuit is turned

off. To either replace the fuse with one of higher value or

wire around it with a coin is to defeat a safety

device designed to

protect you.

.35B Fix It

Attention Danger !

Never open or work on any appliance which is plugged in.

Bring in a SIMPLE small electric appliance which no longer works. (Ex. Hair dryer, curling iron, lamp, toaster, string of tree lights …)

Find the fault. Repair it Complete the following

HYPOTHESIS (hunch or suspicion used start looking for the fault )

____________________________________________________________

DEDUCTIVE REASONING

Point log of the method and reasoning used to find the fault

________________________________________________________________________________________________________________________________

VERIFICATION

________________________________________________________________________________________________________________________________

Tests used to prove it is fixed

________________________________________________________________________________________________________________________________

Job Evaluation

Job: ________________________________

Evaluation Item

Peer Evaluation

Mark

HYPOTHESIS

1 2 3

 

DEDUCTIVE REASONING

2 4 6 8 10

 

VERIFICATION

2 4 6 8 12

 

LEVEL OF DIFFICULTY

. 2 4 8 12

 

QUALITY OF WORKMANSHIP

3 5 8 10

 

TOTALS/ 27

   

3.40 Parallel, (branched paths)

( parallel, alternate path)

.41 How does adding branches affect the current in each branch?

Fact: The brightness of the light is a measure of the current

Set up these circuits and observe and circle the bulb at the right which best represents the brightness.

Conclusion:

The current in a parallel circuit is ________ (unchanged/ more/ less) in each branch when branches are added.

.42 How does adding branches affect the total current in the whole circuit?

Fact: All the current in the alternate circuit paths must pass through the shaded bulb.

The brightness of the light is a measure of the current

Set up these circuits and observe the brightness of the shaded bulb. Circle the bulb at the right which best represents the brightness.

Conclusion:

The total current in a parallel circuit is ________ (unchanged/ more/ less) when more branches are added.

.43 How does a break affect the circuit?

(a) Set up this circuit.

(b) Unscrew then replace a bulb observe what happens to the other bulbs.

(c) Remove then replace a wire form the alternate path part observe what happens to the other bulbs.

 

A break in a branched path affects ___________

 

.44A (Series/Parallel) Current Comparisons

Circuit Key

Current Investigations

Fact: The brightness of the bulb indicates the current.

What to do: Connect each circuit record the results.

Question

Experiment Design

Observation

(Result of experiment)

ConclusionInference

Choose from P166

1. How is the amount of current affected by the number of cells in the circuit?

   

2. How is the current affected by the number of bulbs connected in a one path (that is series) circuit?

   

3

How is the current through a branched (that is parallel) circuit compare with the current through each bulb in a series circuit?

   

4. What difference is there in the total current at the battery source when the bulbs are connected as follows: series, parallel ? (observe at the brightness of the shaded bulb)

   

 

 

.44B Brightness Quiz

This bulb gives "standard brightness" (S)

Apply what you know about series and parallel circuits; choose a predict -ion for the marked bulb from among the following brightness choices:

(a) standard brightness (b) less bright (c) more bright

Darken the oval on the answer sheet which corresponds to the letter of the answer you have chosen.

[1]

(a) standard brightness (b) less bright (c) more bright

[2]

(a) standard brightness (b) less bright (c) more bright

[3]

(a) standard brightness (b) less bright (c) more bright

[4]

(a) standard brightness (b) less bright (c) more bright

[5]

(a) standard brightness (b) less bright (c) more bright

[6]

(a) standard brightness (b) less bright (c) more bright

[7]

(a) standard brightness (b) less bright (c) more bright

[8]

(a) standard brightness (b) less bright (c) more bright

[9]

(a) standard brightness (b) less bright (c) more bright

[10]

(a) standard brightness (b) less bright (c) more bright

[11]

(a) standard brightness (b) less bright (c) more bright

[12]

(a) standard brightness (b) less bright (c) more bright

[13]

(a) standard brightness (b) less bright (c) more bright

[14]

(a) standard brightness (b) less bright (c) more bright

[15]

(a) standard brightness (b) less bright (c) more bright

Answer sheet

(# 1-15 value @2 pt ea = 15*2pt = 30pt)

 

____________________________________________________

 

___ *2 = ___ /30 pts

.45 Usefulness/Application

A) Solving Circuit Problems

Circuit Key

 

Construct the Following

Connection Suggested (series/parallel)

Diagram

1. A circuit that will light two bulbs, A and B, at the same time when a switch is closed. ( If A is unscrewed B goes out also)

Switch _______

(series / parallel)

Bulb (A&B)

(series / parallel)

 

2.. A circuit that will light two bulbs, A and B, at the same time when a switch is closed. ( If A is unscrewed B is not affected and vice versa)

Switch _______

(series / parallel)

Bulb (A&B) ____

(series / parallel)

 

3. A circuit that contains three bulbs, A, B, &C.

If A is unscrewed both B&C go out

If B is unscrewed both A&C stay lit. If C is unscrewed both A&B stay lit.

 

Bulb A _______

(series /parallel) with B&C

Bulb A&B _____

(series /parallel) with each other

 

4. A circuit with two bulbs and two switches P&Q (Start with both switches P&Q open both lights off)

Close switch Q, only one light turns on.

Close both switches P&Q both bulbs light

 

 

 

I

If switch P is now opened then only one light goes out

 

 

 

 

 

 

Switch Q and one light are in

(series /parallel) with each other.

and

(series /parallel)

with the other light and switch P

Switch P and one light are in

(series /parallel) with the other light but in

(series /parallel)

with switch Q

 

5. A circuit with two bulbs and two switches ,P&Q are connected. When either switch P or Q are closed both bulbs come on.

 

(If both P&Q closed the bulbs light If both P&Q open the bulbs do not light)

Switch P&Q

(series /parallel) with the two bulbs

Switch P&Q

(series /parallel) with each other

 

 

 

 

.45A Perplexing Puzzles

Julie and Jennifer's Puzzle

Julie and Jennifer were discussing the switching circuit of a very long hall at school. The hall lights can be turned of or on from either end of the hall. Here are the two competing schematics being discussed as possible wiring for the switches.

.1 Write a comparison (in point form) for the operation of the switches in these two circuits.

.2 State which circuit was most likely chosen as the hall light switching circuit and clearly defend your choice.

.3 Set up the circuits and verify your hypothesis

Jeff's puzzle

Tom made a circuit that contained a dry cell, a light bulb and two, "switches" There were two contacts "A" ," B" and a pivoting bar between, on the first switch. On the second switch there are contacts "C", "D" and a pivoting bar between the two contacts. Here is how it worked.

(a) Jeff moved the first switch from A to B the light went off.

(b) Then he moved the second switch from D to C and the light went on.

(c) After that he moved the first switch from B to A-- light went off.

(d) Then Jeff moved the 2nd switch from C to D-- light went on.

2.1 Complete the connecting wires from A,B, (SW-1) to D, and C of SW-2 in Jeff's circuit.

2.2 Where have you used something that works like this before?

Tom's puzzle

Tom made a circuit that contained a dry cell, a light bulb and two, "switches" There were two contacts "A" ," B" and a pivoting bar between, on the first switch. On the second switch there are contacts "C", "D" and a pivoting bar between the two contacts. Here is how it worked.

(a) Tom moved the first switch from A to B the light went on.

(b) Then he moved the second switch from D to C and the light went off.

(c) After that he moved the first switch from B to A-- light went on

(d) Then he moved the 2nd switch from C to D-- light went off.

Complete the connecting wires from A,B, (SW-1) to D, and C of SW-2 in Jeff's circuit.

Where have you used something that works like this before?

______________________________________________________________________________________________________________________________

 

 

Mr. Carson's Puzzle

Circuit (C1) Circuit (C2)

0.1 How is circuit (C1) different from circuit (C2) ?

_______________________________________________________________

0.2 If you wanted to light B1 without lighting B2 which circuit would you choose?____________________

0.3 Which circuit has a bulb which glows brighter than the other bulbs? ______________________

0.4 Which circuit could be overloaded by adding more bulbs in the same pattern?________________

 

.45B Cryptogram Summary

Cryptogram Key

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o pq r s t u v w x y z

n o p q r s t u v w x y z

Finding Parallel Circuits

It is easy to test a path to see if it is in parallel with another. Just

disconnect the path in

question and see if the

other parts of the

circuit continue to work.

You can recognise parallel circuit connections if one

part can be disconnected

and an alternate path in

the circuit continues to

work

Answers .45B Cryptogram Summary

Finding Parallel Circuits

It is easy to test a path to see if it is in parallel with another. Just

disconnect the path in

question and see if the

other parts of the

circuit continue to work.

You can recognise parallel circuit connections if one

part can be disconnected

and an alternate path in

the circuit continues to

work

.45C Advantages of Parallel Circuits:

Parallel connections have an advantage in connecting appliances and in switching circuits.

Parallel wiring of circuits allow the following:

[1] Each appliance works independent of

the others .

[2] Switches can turn lights on or off from

opposite ends of

long halls or large rooms.

 

Answers: .45C Cryptogram Summary

Advantages of Parallel Circuits:

Parallel connections have an advantage in connecting appliances and in switching circuits.

Parallel wiring of circuits allow the following:

[1] Each appliance works independent of

the others .

[2] Switches can turn lights on or off from

opposite ends of

long halls or large rooms.

 

3.50 Overloaded Circuits

.51 The Long and Short of Circuits

To overload a circuit is to allow to much current through it. The path will then overheat, melt or catch fire.

The following diagrams show some causes for overloaded circuits.

As you learn to connect circuits the following are some common faults to avoid.

.51A This common fault is called a short.

It is simply a path in the circuit without an energy converter (appliance).

To much current flows in the circled path and it overheats.

These faults may look like the following circuits:

Circle and name the problem

.51B Shorts are also caused by switches or fuses connected in parallel paths

These kinds of problems are usually mistakes made by either electricians or unqualified persons who attempt wiring.changes at home.

.51C Short caused by an, "octopus", connection.

Each path receives current as if it were the only path The current adds up for the total path The fuse overheats and melts.

Circle the problem

.51D Summary (Disadvantages of Parallel Circuits)

Cryptogram Key

a b c d e f g h i j k l m

a b c d e f g h i j k l m

n o pq r s t u v w x y z

n o p q r s t u v w x y z

 

Disadvantages of parallel circuits:

These circuits can be overloaded with electric current by

continuing to add alternate

paths to the circuit . Each

new path carries electric current as if it were

the only path in the

circuit. Adding appliances in this way

increases it in the

total circuit path from

the battery.

 

Answers: .51D Summary (Disadvantages of Parallel Circuits)

These circuits can be overloaded with electric current by

continuing to add alternate

paths to the circuit . Each

new path carries electric current as if it were

the only path in the

circuit. Adding appliances in this way

increases it in the

total circuit path from

the battery.

.51E Managing a safety problem:

This is a safety problem. It can be managed with

safety devices like

fuses and circuit

breakers.

To prevent the overheating of circuits with too much current we

put a fuse in the main

line from the energy

supply (Series with the energy supply) Then if parallel

paths ( for example to many alternate paths) draw to much electric

current the fuse blows and cuts off

the supply

 

Answers:.51E Managing a safety problem:

This is a safety problem. It can be managed with

safety devices like

fuses and circuit

breakers.

To prevent the overheating of circuits with too much current we

put a fuse in the main

line from the energy

supply (Series with the energy supply) Then if parallel

paths ( for example to many alternate paths) draw to much electric

current the fuse blows and cuts off

the supply