This experiment demonstrates the charging and discharging of a capacitor. The charge/discharge time is controlled by resistors on either side of the capacitor. These resistors control the flow of electricity going to the capacitor (charge) and from the capacitor (discharge). The discharge is visualised by the LED in the experiment. The slower the LED dims, the larger the resistor is (ohms) that is controlling the discharge from the capacitor. The charge/discharge times are proportional to both the capacitance (amount of voltage a capacitor can hold) and the resistance in the charge/discharge path. In the below videos titles, the numbers followed by K are the charge and discharge resistor values (respectively), and the last number is the capacitor's capacitance in micro farads.
Monday, November 19, 2012
Elenco's PK-201 Experiment #7: Water Detector
This experiment shows that water will conduct electrical current. But, resistance can vary by amount and purity of the water. In the first picture, tap water is used to conduct electrical current. The LED is dimly lit because the water has a high resistance. In the last picture, salt was added to the same water causing the LED to become brightly lit. To conclude, water will conduct electrical current, but pure water has a higher resistance then water with salt dissolved in it. |
| Fresh Water (Dim LED) |
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| No Water (off LED) |
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| Salt Water (Bright LED) |
Elenco's PK-201 Experiment #6: Combined Circuit
In this experiment there are two LED's (Left and Right). The left LED is connected to a 3.3k ohms resister, and, in addition, to a variable resistor (0 to 50k ohms). The left LED is connected only to a 10k ohms resistor. The first picture, shows a lighted left LED and a very dim right LED because most of the current is flowing in the direction of least resistance. The variable resistor is set to 0 ohms, which leaves only a resistance of 3.3k ohms. Where as the right LED has a higher resistance of 10k ohms. The second picture, shows both LED's lighted because the Variable resistor is set to give equal resistance as the right LED (10k ohms) resistance. In the last picture, the right LED is the brightest because the variable resistor is set to the maximum resistance of 50k ohms. Like experiment #5 current is still flowing in multiple paths, but nearly all the current is flowing towards the path of least resistance.
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| Current is flowing through left LED |
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| Equal resistance current is divided between both LEDs |
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| Current is flowing through right LED Further Study: Questions and Answers on Physics What is a Parallel Circuit? |
Sunday, November 18, 2012
Elenco's PK-201 Experiment #5: Comparison of Parallel Currents
This experiment is demonstrating that current can move along multiple paths in a circuit. More over, that the current is proportional to the resistance of said circuit. |
| 100k ohm resistor |
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| 1k ohm resistor |
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| 10k ohm resistor |
Elenco's PK-201 Experiment #4: Parallel Pipes
In general, this experiment shows that the more resistors that are in parallel in a circuit, the lower the total resistance; subsequently, more current will flow through the circuit. The formula and calculations are at the bottom showing the total resistance in each example.  |
| 3.2k ohm's |
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| 2.5k ohm's |
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| 770 ohm's |
Friday, November 16, 2012
Elenco's PK-201 Experiment #3: Resistors In Series
Resistors in a series add together to increase the total resistance of a circuit. In addition, the larger resistor in that series will control the flow of current in said circuit. |
| 3.3k and 100k ohm resistors = 103.3k ohms |
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| 3.3k and 10k ohm resistors = 13.3k ohms |
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| 3.3k and 1k ohm resistors = 4.3k ohms |
Elenco's PK-201 Experiment #2: The Brightness Control
In this experiment the focus is understanding the Variable Resistor (0 to 50k ohm). A device that has three pins (terminals to run electrical current through) and a dial. The dial is for increasing or decreasing resistance. When the dial is set to a minimum, the resistance is 0 ohms. Turn the dial to maximum then the resistance is set to 50k ohms. In the pictures, the Variable Resistor is wired from the center pin to left pin, center pin to right pin, or left pin to right pin. This means, depending on how the Variable Resistor is wired, that the resistance is measured between two of the three pins (left to center, right to center, or left to right). In the picture left to right, the resistance is between the left and center post. By turning the Variable Resistor to the right, one would increase the resistance hence dimming the light. In the picture right to left, the resistance is from right to center. By turning the resistance to the left, one would increase the resistance hence dimming the light. In the last picture, the resistance is 50k ohms. This is because the wiring is from left post to right post causing a lose of the variable attribute.  |
| High Resistance (Left to Right) |
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| Low Resistance (Left to Right) |
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| High Resistance (Right to Left) |
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| Low Resistance (Right to Left) |
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| Full Resistance (None Variable) |
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