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1.1

Minor Versionm

by Kailash NR

Introduction

Make a conductive paint and use it to create your own resistor.

    • Scissors have functional sharp edges. Contact may result in injury. Always keep blades away from fingers and body. Handle with care.

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  1. Note the terminals(positive and negative) of the two AA Cells.
    • Note the terminals(positive and negative) of the two AA Cells.

    • Now stretch the cycle-tube band over a cell from one terminal to another. Do the same for the other cell.

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    • Now push the head of a safety pin into the space between the positive battery terminal and the band.

    • Repeat this for the other cell.

    • Push the positive terminal "pin" of one cell into the negative of the other cell. This will result in a 'U' shape with one pin sticking out.

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    • At this point your probe should look like this, as shown in the picture.

    • Cut the ice-cream stick into 2 rectangular pieces of about 4 cm each.

    • Push one of the pieces into the space between the band and their cells, on one side.

    What are these "different materials"? Give a few suggestions/examples....

    Procheta Mallik - Reply

    • Do the same on the other side of the batteries as well.

    • Bend the negative pin of the LED at a right angle about 1 cm from its base.

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    • Now insert the negative pin in-between the open negative terminal of the battery and twist it up around the band.

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    • Take the wires and remove a bit of insulation from both the ends.

    • Then take one end of wire and pass it through the loop on the positive pin. Twist it to make a secure electrical connection.

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    • Tie the other wire to the positive terminal of the LED. Then bend it around the ice-cream stick piece.

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    • The wires are now your test leads.

    • If the LED does not glow, it is an example of a negative result, in this case the material is an insulator.

    • If the LED glows, it is an example of a positive result, in this case the material is a conductor.

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    • The connections between the battery and safety pin might be loose,in that case hold the two terminals with your thumb and index finger for a better connection.

    • Make sure all the connections are clean and stable, otherwise the current will not flow.

    • To ensure proper connection, wind the wire several times over the material.

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    • Make a table and note down if the bulb glows for a particular material or not.

    • Classify the materials depending on whether the bulb glows or not, into conductors and insulators.

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    • Did you notice any common characteristic(s) for the materials that conducted electricity? What about those that didn't?

    • Could you find any difference in the brightness of the LED depending on the conducting material you tested?

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    • Be mindful of the battery terminals, they can heat up or momentarily spark if an electrical short occurs.

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    • Start with about half gram of graphite power in a small saleable container.

    • To this add 2 drops of white (PVA) glue.

    • Use the dropper to measure out 1 ml of water and add it to the mixture.

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    • Use the dropper to stir the mixture till it's of an even consistency and is free of lumps.

    • The paint is now ready to use. For long term storage, dilute it with more water and store in an air tight container.

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    • You'll need an ice-cream stick and two pieces of copper tape that are 2.5 cm each.

    • Peel the paper cover off the tape to expose the stick side.

    • Stick the tape on one end of the ice-cream stick .

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    • Wrap the tape around and stick it back to itself.

    • Repeat the same steps to tape the other end of the stick as well.

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    • Measure out 0.5 ml of the paint with the dropper.

    • Carefully draw a line from one copper strip to the other, dispensing most of the paint as you do so.

    • Make sure both ends of the paint line touch the copper strips.

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    • Now smear out the paint on the surface of the stick till there is a uniform and uninterrupted trail of paint between the copper strips.

    • Cover about half the width of the tape pieces with paint as well. This will ensure good electrical contact between the copper terminals and the graphite.

    • Now leave the stick undisturbed to dry, this can take upto an hour, depending on the ambient temperature . When its done the graphite layer will be more grey than black in colour and have a slight metallic glint to it.

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    • Set up the conductivity probe as shown in this guide. This is a simple circuit consisting of an LED that will help test the conductivity of the strip.

    • Close the circuit with no load connected, just to get a feel for the maximum brightness of the LED.

      • If you are using a Red LED with brand new (unused) batteries, it is recommended that you do not perform this check as the LED may burn out.

    • Connect the two leads of the tester to the copper strips on either end of the stick. The LED should be illuminated, if a little dimly.

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    • LED connected directly.

    • LED connected through the graphite stick.

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    • The connections between the battery and safety pin might be loose,in that case hold the two terminals with your thumb and index finger for a better connection.

    • Make sure all the connections are clean and stable, otherwise the current will not flow.

    • Ensure proper connection to the copper contacts.

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Finish Line

Kailash NR

Member since: 05/02/2017

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