Electricity - Spigot Science

Science ConnectionHow to Draw a Circuitthat Really Works!by Brooke ReedlunnLED lightGraphite lineAlligator clipsIf you thought making a circuit had to be complicated...thinkagain! You can DRAW a circuit thatreally works. Here is what you need to get started:Materials:2 alligator clips and wiresLED LightGraphite pencil (Softer pencils work better becausethey make a darker line. Try 2B or 3B.)Paper9V batteryTapeExperimental Procedure:1. Starting at the edge of the page, take the graphitepencil and draw a thick line, the thicker andshorter, the brighter the LED will be. The graphiteline will be one of the “wires” in the circuit.2. Starting at the edge of the page, about an inchaway from the first line, draw another thick linewith the graphite pencil. This is the other “wire”in the circuit. Don’t connect the two lines butleave a space of about an inch between them inwhich to put the LED.3. The circuit can take any shape you want; justdon’t cross lines or make them long.4. Connect the wires to the negative and positiveterminals on top of the 9 Volt battery.5. Clip the battery to the paper so that each of thealligator clips is on top of one of the graphitelines at the edge of the paper. You may have totest it to see which side it positive and which isnegative.6. Touch each of the LED wires to one of thegraphite lines, filling the gap that is left in themiddle of the circuit. With some jiggling andtweaking the LED should light up.7. Keep the LED lit by taping it in place so its wireskeep touching the circuit.Why does this work?It doesn’t seem that this should work, but here isthe science behind it: Pencils are made with graphite,which is conductive. It is not a good conductor likecopper, but electrons can still flow through it.Graphite is also a resistor. That means it restricts theflow of electrons and decreases the voltage as electricityflows through it.In this circuit, we need graphite to work as a conductorand resistor. It has to work as a conductor tocarry electrons to the LED and make it light up. Butit also has to be a resistor because 9 volts of electricityis too much of a charge for an LED and woulddestroy it. By the time the charge of 9 volts of energygets to the LED, it is closer to the 3.5 volts that anLED needs to light up. Try making your circuit lineslonger and shorter to change how much energy getsto the LED. Experiment with it and have fun!Spigot Science - http://www.spigotscience.com 12 Electricity