PHYSICS
Lab 2 - Capacitance

# On your lab bench you will find a high capacity

• Notes
• 9
• 100% (1) 1 out of 1 people found this document helpful

This preview shows pages 4–7. Sign up to view the full content.

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

This preview has intentionally blurred sections. Sign up to view the full version.

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
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.

This preview has intentionally blurred sections. Sign up to view the full version.

This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern