This preview shows pages 75–78. Sign up to view the full content.
After a few moments, open the circuit. Is the capacitor charged or not? To determine if the capacitor is charged, carefully (and safely) remove the battery from the circuit and reconnect the circuit without the battery. With only the capacitor, and bulb (no battery) 75
has intentionally blurred sections.
Sign up to view the full version.
QUALITATIVE CAPACITORS – 1202Lab3Prob3 in the circuit, will the bulb light if you close the circuit and the capacitor is charged? Uncharged? Try it. Was the capacitor charged before you closed the circuit? Was the capacitor still charged long after the circuit was closed? Use conservation of energy to explain your results. CONCLUSIONWas your friend right about how the brightness of the bulb changed over time? Sketch a qualitative graph of the brightness of the bulb as a function of time after you complete the circuit. How does this compare to your prediction? 76
PROBLEM #4: QUANTITATIVE CAPACITORSYou and a friend are discussing how ion concentrations on either side of a cell membrane change with time. In particular you want to investigate how ions (say Na+) migrate and how voltage across the membrane builds up over time. Now you are wondering how the properties of the membrane affect the migration process. You decide to model the cell membrane, very crudely, as a capacitor in series with a light bulb and a battery. A capacitor can be thought of as a device used to hold separated charges (similar to the cell membrane). You decide to get a quantitative understanding of the rate at which a capacitor charges by using a capacitor in series with a light bulb and battery. How does the time that the light bulb is lit depend on the capacitance of the capacitor connected in series with it? NOTE: This problem, and the problems Qualitative Capacitors and Rates of Energy Transfer in RC Circuitsare fundamentally similar. This problem involves a quantitative analysis of an RC circuit, Qualitative Capacitorsinvolves a qualitative analysis, and Rates of Energy Transfer in RC Circuitsanalyzes RC circuit behavior from the point of view of energy transfer to or from the capacitor.Read Sternheim & Kane sections 16.4, 16.9, 17.7 and 18.4. EQUIPMENTBuild the circuit shown using wires, bulbs, capacitors, and batteries. Use the accompanying legend to help you build the circuit. You will also have a stopwatch