On your lab bench you will find a high capacity

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On your lab bench you will find a high capacity capacitor (value: 10F) as well as a variety of resistors. Locate these and verify their values (these will also be used for the subsequent section). Make sure that the capacitor is fully discharged. Do so by connecting a wire to the two ends of the capacitor itself. This will allow the charge to flow from one plate to the other (this may take 30 seconds or so). 4
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Figure 1: Example of common capacitors. Locate one of the light bulbs on your Electronics lab board. Using your DMM measure its resistance. It should be approximately 2 - 10Ω. On the Electronics Lab Board connect the light bulb in series with the 10F capacitors as well as the 10Ω resistor (thus the total resistance will be the sum of the 10Ω resistor and that of the bulb). Connect the Signal Generator to the two on-board banana plug jacks and attach the series of components to them. You should have a circuit equivalent to Figure 2. Figure 2: Driven RC Circuit (series) Configure the Signal Generator to output a DC Voltage of 5V and de-select ‘Auto’ in the Signal Generator window. Click ‘Start’ in DataStudio and when you’re ready click ‘On’ and note the time (in seconds). The bulb should light and then slowly dim. You’re now charging the capacitor. Once the bulb no longer appears to emit light, note the time and click ‘Off’. How long did it take for the bulb to dim? Now that there is no voltage applied, the capacitor should be discharging. What does the bulb appear to be doing? Once the bulb has gone dim again note the time. How long did it take for the bulb to go out this time? Repeat these steps again but place another 10Ω resistor in parallel with the first. Thus your total resistance is now 5Ω + R bulb . 5
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Compare the recorded times. How does the change in resistance compare to the change in time it took to dim the bulb? Note the bulb also contributes to the total resistance of the circuit. Based on what you know about the bulb at what point in time is the current in the circuit the greatest? At what point is it the lowest? Do you think current is still flowing after the bulb appears to go out? Compare the current in the circuit when the capacitor is charging to that when it is discharging. Does it exhibit similar behavior, does it flow the same direction, is it of the same magnitude, etc? 8 RC Circuit (quantitative) Now, to look more quantitatively at RC circuits. A capacitor is a non-linear device - in other words, the rate at which it charges and discharges is dependent on the amount of charge already present on the capacitor. This is implied by the theory as per Eqs. 4 and 5, and in this section you will explore this experimentally in detail. Specifically you will verify the time constant’s ( τ ) dependence on R and C as well as the exponential model describing voltage.
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