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Conductance

EXPERIMENT 3

19

Conductivity
tester

YOU WILL NEED

+ your humidity detector

+ and additional household

items such as a key, eraser,
coin, pencil, toys

HERE’S HOW

1. Get the items ready that you will

want to test.

2. Hold the two bare ends of the long

wires of your humidity detector up
to the key, eraser, coin, etc.

If the materials are conductive, the

green LED will light up; if they do

not conduct electricity, the red LED

lights up.

So not only can your circuit signal

the conductivity of water

, it can

also show what other objects are

capable of conducting current

.

C

WHAT’S HAPPENING?

Note!

Of course, during all your

experiments you have to

be sure that the bare wire

ends do not touch each

other — otherwise your

sensor will not work.

LED1

LED2

T1

+

–

T2

A

A

C

C

R1

220 kΩ

R2

100 kΩ

R3

470 Ω

R4

22 kΩ

R5

3.3 kΩ

R6

470 Ω

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Summary of Contents for Electronics

Page 1: ...ARNING Science Education Set This set contains chemicals and or parts that may be harmful if misused Read cautions on individual containers and in manual carefully Not to be used by children except under adult supervision ...

Page 2: ...ed 1 4 Pushbutton 1 000367 5 Wire bridges short 10 pieces 1 000282 6 Wire bridges long 10 pieces 1 000292 7 Wire connectors 2 000343 8 Battery clip for 9 volt battery 1 712310 Please check all the parts against the list to make sure that nothing is missing If you are missing any parts please contact Thames Kosmos customer service Checklist Find Inspect Check off Additional things you will need 9 v...

Page 3: ...m Learn how alarm systems work Timer Switches Pages 28 to 33 Circuits that buy you time Flashers Pages 34 to 41 On Off On Off That s how it works Sensors and Detectors Pages 42 to 48 Sensitive detectors and exciting experiments CHECK IT OUT You will find supplemental information on pages 21 27 22 23 41 47 and 48 ...

Page 4: ...rrect polarity direction Never recharge non rechargeable batteries They could explode Take rechargeable batteries out of the experiment kit box before recharging them We assume no liability against any damage of any kind that may arise from the experiments In addition we offer no guarantee that the circuits and procedures described in this manual are free of copyright protection The instructions a...

Page 5: ...tion location for the recycling of elec trical and electronic equipment The symbol on the product in structions for use or packaging indicates this The materials are reusable in ac cordance with their designation By reusing or recycling used de vices you are making an impor tant contribution to the protec tion of the environment Please consult your local authorities for the appropriate disposal lo...

Page 6: ...rforming the experiments In electronics you usually work with a base plate sometimes called a breadboard or simply board The electronics board in your kit will serve this purpose It contains openings for the contact clips and for forming the circuit assembly You will be inserting the components into these contact clips in order to connect them to one another electronically Contact clips Introducin...

Page 7: ...iniature electronic lights can overheat for example and be destroyed if they get too much current That s why you need resistors which act like little current brakes Their ability to put the brakes on current is indicated in ohms Ω and kilohms kΩ The more ohms a resistor has the greater its braking Capacitors are able to store electric current just like a battery Their capacitance or how much curre...

Page 8: ... larger ones which can be used to amplify small signals In the model we can picture that as small waves in the base channel turning into larger ones in the collector emitter channel Transistors are used for switching and amplifying electrical currents and voltages Each of the two transistor modules in your kit has three terminals Collector C Base B Emitter E Always be sure to insert the sensitive ...

Page 9: ...aning that they only work in one direction When turned the wrong way they won t let current through and they also won t light up Diodes work similarly to the model with the water and the gate If the current comes from the wrong direction the mechanism prevents the water from flowing through If the water comes from the other direction the gates open up and the water flows through That corresponds t...

Page 10: ...he next them as sensors and alarm wires for example The pushbutton is a kind of current switch serving to open or close a circuit A regular switch will open or close a current flow and keep it in that state A pushbutton on the other hand will open or close the The wire bridges are made of thin copper wire which is a good current conductor They connect the other kit components by You will find two ...

Page 11: ... it wouldn t be good for anything The battery clip will help to conduct electrical current from the battery to your circuit It is easily mounted onto the battery with only one orientation being possible relative to the battery terminals The current will then move through the two loose wires to your circuit Battery clip B C T E B C E R 3 3 kΩ 10 k 10 F C LED 100 nF U V S T O P R C Ta A C A 9 V M NT...

Page 12: ...highly conductive metal parts with holes in the top You can insert the components terminal wires or connecting wires the wire bridges into the holes and pull them out again easily Your kit contains 17 contact clips to insert into the board It s easy Just hold the sides of the contact clip between thumb and forefinger and press them gently together Then simply insert the sides into the openings Whe...

Page 13: ...ody for example if you accidentally touch the wire There are cuts through the insulation near both ends of the wire forming loose sleeves that you can easily slide off Bending the LED terminal wires You will also have to bend the LED terminal wires to be able to insert them into position later on To do that proceed just as you did with the wire bridges Place the LED on top of the sketch to the rig...

Page 14: ...looking for all the parts and placing them in the parts compartment The right polarity is important Always install the capacitors the right way around The assembly drawing shows exactly how Also be sure to use the right capacitance value 10 µF or 100 µF Otherwise the circuit won t work right Insert the LEDs correctly The LEDs have one long and one short terminal wire The short terminal the cathode...

Page 15: ... positive wire coming from the battery clip is red while the negative wire is black The same colors are used in the assembly drawing as well In the drawing you will also see a and a sign next to the connections Using the right resistors The resistors protect components such as the LEDs against excessive current which might destroy them So always be sure to install the right ones ...

Page 16: ...e symbols by taking a look at the section with the component descriptions This kind of schematic circuit diagram is much easier and quicker to draw than a complete circuit board illustration For each experiment you will find both a pictorial illustration as well as its corresponding circuit diagram As an example this is the circuit diagram for a battery tester Experiment 18 9V T1 R 4 470 Ω R 3 470...

Page 17: ...ations all of the components are shown and labeled exactly as described on pages 2 to 8 So if you ever aren t sure exactly which component you are supposed to use you can check the front of this manual This shows the illustration corresponding to the battery tester Experiment 18 circuit board on the previous page Note The colors of the components can sometimes be different from how they are shown ...

Page 18: ...16 Conductance Would you like to know which things are good conductors of electricity and which are not Then assemble your humidity detector and start by testing the conductance of water ...

Page 19: ...glass with tap water 3 Dangle the two long wires A and B into the glass What happens 4 Now pull the wires back out of the glass 5 Hang the two wires in the water again and wait a couple days What happens when the water evaporates As soon as the two long wires touch the water the green LED lights up an indication that there s enough water present If you pull one of the wires out of the glass the gr...

Page 20: ... a window in your room 2 Insert the bare ends of the long wires A and B of the humidity detector into the blotting paper strip Now you just have to wait for a good rain When it starts to rain the blotting paper soaks up water and your electronic circuit reacts to the moisture the green LED lights up When the rain stops the blotting paper dries again and the red LED comes on C WHAT S HAPPENING EXPE...

Page 21: ... coin etc If the materials are conductive the green LED will light up if they do not conduct electricity the red LED lights up So not only can your circuit signal the conductivity of water it can also show what other objects are capable of conducting current C WHAT S HAPPENING Note Of course during all your experiments you have to be sure that the bare wire ends do not touch each other otherwise y...

Page 22: ...touch Before you start the lie test the detector s red LED should be lit 2 Start by asking your test subject some harmless questions and then proceed to trickier and more awkward ones As long as the red LED stays lit the test subject is telling the truth But when the green LED lights up he or she might be lying When people lie their palms start to sweat This film of sweat on the palms causes enoug...

Page 23: ...omething like Now he s starting to sweat Your humidity detector reveals the literal truth behind that saying In everyday language a lie detector refers to a device that measures and displays bodily signals such as blood pressure pulse breathing rate or the electrical conductance of the skin during an interrogation In technical terms the device is not called a lie detector but a polygraph multi wri...

Page 24: ...s Alarm Systems Did someone steal your favorite candy bar again Try building a simple alarm system that you can use to secure your door or window That way you will be able to see if someone has been in your room while you were away ...

Page 25: ...g wire 3 When you hook up the battery and push briefly on the pushbutton the red LED LED2 goes out 4 The alarm system is now ready for you to test it by pulling the long wire out of the circuit As soon as the connection between the A and B contact clips is interrupted the red LED turns on Alarm And the green LED only comes on briefly when the alarm is shut off C WHAT S HAPPENING 9V T2 T1 R 1 470 Ω...

Page 26: ...dy again by pressing the pushbutton Can you figure out why you might not want the LED to go out again even when you re establish the original connection The explanation is simple If that weren t the case an intruder could simply turn off the alarm himself So if instead of the long wire you use a thin tripwire that an intruder breaks it won t do him any good to mend the wire again C WHAT S HAPPENIN...

Page 27: ... x 7 cm Glue the foil to the cardboard strip 3 Attach the cardboard with the foil to the door at the same height as the two wire ends that you already attached to the doorframe Be sure that when the door closes the two wires from terminals A and B touch the aluminum foil 4 Open the door and see what happens The aluminum foil is a good conductor of current If the door opens the flow of current is i...

Page 28: ...ERE S HOW 1 Pull the long wire out of contact clip A 2 Briefly touch the free end of the wire against the base terminal B of the right T2 transistor What do you notice 3 Now press the pushbutton Do you notice a change Flip flop Your alarm system is a modified flip flop circuit A flip flop is a fully automatic electronic switch of a type that is very often used in electronic equipment such as in th...

Page 29: ...dly flashing alarm light will usually drive off an intruder pretty quickly because it attracts a lot of attention Intruders can often even be frightened just by seeing that an alarm system has been installed Holdup alarm systems serve to respond to break ins or notify a security service or the police in case of a stickup Access control There are also other methods though to deny access to unwanted...

Page 30: ...Timer switches Timer switches can open or close circuits in a delayed manner What role does an electrolytic capacitor play in this Perform the experiments in this chapter to find out 28 ...

Page 31: ...r switch is ready 2 Press once on the pushbutton When you first connect the battery the green LED is lit up while the red one is switched off Your timer switch is ready once the red LED comes on by itself and the green one goes out As soon as you press the pushbutton the green LED comes on and the red one goes out After a cycle time of just under a second the timer switch returns to its starting s...

Page 32: ...ne used in Experiment 9 the result is about ten times the cycle time C WHAT S HAPPENING HERE S HOW 1 Replace the 10 µF capacitor in your timer switch with the 100 µF one 2 Connect the battery and wait until the timer is ready 3 Press once on the pushbutton What has changed since Experiment 9 9V T2 T1 R 2 22 kΩ R 1 3 3 kΩ R 5 220 kΩ R 3 470 Ω R 4 100 kΩ 100 µF C 1 Ta 1 LED 1 R 6 470 Ω LED 2 LED1 LE...

Page 33: ...button with your middle finger which has the farthest reach You will see that you act like a large resistor Am besten feuchtest du die Finger vorher an sonst kann es lange dauern bis etwas passiert Depending on the dampness of your skin and the pressure of your finger the cycle time will be shorter or longer Of course you can also perform this experiment with the 10 µF capacitor In that case you w...

Page 34: ...ain delay so the proper owner has enough time to turn the system off after opening the door A pedestrian light should only switch from red to green a few seconds after the button has been pushed To save electricity stairway lights in apartment houses should only shine for a few minutes before turning themselves off 32 TIMER CLOCKS A timer clock is a clock that switches an electrical contact on or ...

Page 35: ...Brown 1 1 0 1 Red 2 2 00 2 Orange 3 3 000 Yellow 4 4 0 000 Green 5 5 00 000 Blue 6 6 000 000 Purple 7 7 Gray 8 8 White 9 9 Gold x 0 1 5 Silver x 0 01 10 No Ring 20 brown Example 100 Kiloohm 100 000 Ohm 1 0 0000 5 black yellow gold Black 0 0 Color 1st Ring 1st Digit 2nd Ring 2nd Digit 3rd Ring Zeros 4th Ring Tolerance Brown 1 1 0 1 Red 2 2 00 2 Orange 3 3 000 Yellow 4 4 0 000 Green 5 5 00 000 Blue ...

Page 36: ...F l a s h e r s How does a flasher work What role do resistors play How can you assemble a flashing alarm system All these exciting questions will be answered in this chapter 34 ...

Page 37: ...lip and additional household item 9 volt square battery HERE S HOW 1 Assemble your circuit 2 Connect the battery and watch what happens As soon as you hook up the battery the green and red LEDs start to light up in turn switching quickly every one or two seconds C WHAT S HAPPENING 9V T2 T1 R 2 220 kΩ 10 µF C 2 100 µF C 1 LED 1 R 4 470 Ω R 3 470 Ω R 1 22 kΩ LED 2 LED1 LED2 T1 T2 A A C C R2 220 kΩ C...

Page 38: ... and remove the red wire from the positive battery terminal Park it in one of the board s compartments 2 Now make the following changes in accordance with your new assembly plan Remove the 22 kΩ resistor R1 and the 220 kΩ resistor R2 In their place insert the 3 3 kΩ resistor for R1 and the 22 kΩ resistor for R2 3 Replace the red battery wire What do you notice 9V T2 T1 R 2 22 kΩ 10 µF C 2 100 µF C...

Page 39: ...irst when you exchange the resistor nothing happens at all except for the green LED lighting up But then the red LED flashes quickly while the green one briefly goes out So by switching the resistors you changed the circuit so that the red LED blinks just briefly C WHAT S HAPPENING 9V T2 T1 R 2 220 kΩ 10 µF C 2 100 µF C 1 LED 1 R 4 470 Ω R 3 470 Ω R 1 100 kΩ LED 2 LED1 LED2 T1 T2 A A C C C1 100 µF...

Page 40: ...s C1 and C2 in your circuit Make sure that their poles are turned as shown in the illustration Does the flash pattern change 2 You can also try switching the R1 and R2 resistors and then return C1 and C2 back to their original posi tions 3 Try all the flash combinations you can get by switching the two resistors R1 and R2 and the two capacitors C1 and C2 Make a note of which positions produce shor...

Page 41: ...stor 2 Insert the long wires 3 Take the two bare wire ends between your moistened thumb and forefinger What do you observe 9V T2 T1 R 2 220 kΩ R 1 3 3 kΩ 10 µF C 2 100 µF C 1 LED 1 R 4 470 Ω R 3 470 Ω LED 2 Depending on how moist your fingers are the LEDs will blink faster or slower So you can regulate their flashing speed by using your skin resistance C WHAT S HAPPENING LED1 LED2 T1 T2 A A C C R2...

Page 42: ... again the circuit starts to flash Alarm That s how easy it is to turn your flasher circuit into an alarm system C WHAT S HAPPENING HERE S HOW 1 Insert a small wire bridge into the contact clips at the bottom left What change do you notice 2 Remove the wire bridge again 9V T2 T1 A B R 2 220 kΩ 10 µF C 2 100 µF C 1 LED 1 R 4 470 Ω R 3 470 Ω R 1 100 kΩ LED 2 Tip Instead of the small wire bridge of c...

Page 43: ...als For example a blinking light at a pedestrian crosswalk or at a railroad crossing or in a shop window display And of course any motor vehicle has a blinker too A blinker or turn signal is a light that is used to signal a change in driving direction to other drivers So all in all flasher circuits are very common CHECK IT OUT Flashers 41 ...

Page 44: ...lden 42 Sensors Detectors Dimly glimmering LEDs electronic wizardry and heat sources now aren t you curious to find out about all these things So let s get started right away with the experiments in this chapter ...

Page 45: ... only glimmer weakly If so take that as a warning It may mean that the experiments in this chapter won t work with that battery Or does the LED not light up at all If that s the case check to be sure that none of the components are installed wrong or whether there s a wire bridge missing If everything looks good you can be sure that the cause is a dead battery That s how you can tell whether a bat...

Page 46: ...electrical field created by static electricity C WHAT S UP HERE S HOW 1 Assemble the components as shown in the circuit diagram At terminal B insert a long wire vertically like an antenna 2 Make an O with your thumb and forefinger and lower this O over the antenna without touching it Shuffle or rub your feet a few times against the floor Do you notice anything 9V T2 A B T1 R 2 470 Ω R 1 470 Ω LED ...

Page 47: ... last person with his or her finger on contact clip B 3 Now have one of your friends let go of his or her neighbor s hand and then touch the neighbor on the nose or ear What do you see The LED turns on right away This experiment even works well with more than ten people because a tiny stream of electric current flows through the bodies of the entire chain of participants is detected by the electro...

Page 48: ...the ice cube then transistor T2 How does the LED react now When you heat transistor T1 with the warm air the LED gradually becomes darker but when you heat T2 it gets brighter When you cool transistor T1 with an ice cube the LED gets brighter But as soon as you cool T2 it gets darker So you can influence the brightness of the LED by changing the temperatures of the transistors The temperature diff...

Page 49: ...ightest distinctions Electronics can perceive changes in the environment as well particularly through sensors also known as detectors There are detectors for gas temperature humidity sound light and a lot of other things Electronic sensors can also detect things that we cannot perceive at all through our own senses such as electrical and magnetic fields AND SENSORS CHECK IT OUT Sensors Detectors 4...

Page 50: ...en used in electronic devices B A dance in which you move your shoulders in rhythm to electronic sounds C The common name for an old computer diskette What kind of resistor is shown here A a 470 Ω resistor B a 22 kΩ resistor C a 220 kΩ resistor Black 0 0 Color 1st Ring 1st Digit 2nd Ring 2nd Digit 3rd Ring Zeros 4th Ring Tolerance Brown 1 1 0 1 Red 2 2 00 2 Orange 3 3 000 Yellow 4 4 0 000 Green 5 ...

Page 51: ...cus finder p 27 tl Gina Sanders p 22 t Jamiga p 21 tl Jose Manuel Gelpi p 9 Jürgen Fälchle p 47 tr krzysztof siekielski p 1 bl timer switch 28 r lassedesignen p 22 b M S Fotodesign p 47 br Martina Berg p 27 tr miket p 35 milkovasa p 24 Miroslaw Dziadkowiec p 31 misaleva p 47 l Nadezhda Sundikova p 48 N Media Images p 1 bl boy with clock 28 l Perrush p 1 tl boy 16 b Reinhold Föger p 32 33 crossing ...

Page 52: ...712 301 ...

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