the rc circuit

Your work on the rc circuit has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.

Your comment or question:

Initial voltage and resistance, table of voltage vs. clock time:

Voltage vs. clock time would have clock time first, voltage second; clearly you have these in reverse order.

Times to fall from 4 v to 2 v; 3 v to 1.5 v; 2 v to 1 v; 1 v to .5 v, based on graph.

Table of current vs. clock time using same resistor as before, again starting with 4 volts +- .02 volts.

You appear to be reporting voltage instead of current. To measure current, you need to have the meter set to measure amps or milliamps, and the meter has to be in series rather than in parallel, as in previous experiments.

Times to fall from initial current to half; 75% to half this; 50% to half this; 25% to half this, based on graph.

Within experimental uncertainty, are the times you reported above the same?; Are they the same as the times you reports for voltages to drop from 4 v to 2 v, 3 v to 1.5 v, etc?; Is there any pattern here?

Table of voltage, current and resistance vs. clock time:

I don't think you were measuring current. The initial current in this circuit will be on the order of a hundred milliamps or so, and will drop along with the voltage.

Slope and vertical intercept of R vs. I graph; units of your slope and vertical intercept; equation of your straight line.

Report for the 'other' resistor:; Resistance; half-life; explanation of half-life; equation of R vs. I; complete report.

I believe you were using the correct procedure earlier to get the resistances; the only problem was that I don't think you were dividing by current, since I don't think you actually measured the current.

Number of times you had to reverse the cranking before you first saw a negative voltage, with 6.3 V .15 A bulb; descriptions.

When the voltage was changing most quickly, was the bulb at it brightest, at its dimmest, or somewhere in between?

Your observation is correct. As you work through the text, etc., you will see why this is the case, but you deserve a quick explanation here. The reason is the capacitor voltage is determined by the amount of charge on the capacitor, and the current is the rate at which the capacitor is being charged or discharged; so the faster the charge on the capacitor is changing, the greater the current and the brighter the bulb.

Number of times you had to reverse the cranking before you first saw a negative voltage, with 33 ohm resistor; descriptions.

This part is just like the preceding, but the number of cranks changes and you swap the bulb for a resistor. The instructions in the previous part tell you to crank for 100 cranks, then reverse every 5 cranks. At this point in the experiment you do essentially the same thing, but replace the bulb with the resistor. Instead of 100 cranks you crank for a time equal to double the time constant. From the beeping rate you figure out how many beeps this will take; this is so you can just count beeps and not have to watch a clock along with everything else. 1/4 of the time constant is just the time constant, divided by 4. Once you have that number, you figure out how many 'beeps' correspond to that time. Then you proceed as before.

How many 'beeps', and how many seconds, were required to return to 0 voltage after reversal;; was voltage changing more quickly as you approached the 'peak' voltage or as you approached 0 voltage; 'peak' voltage.

Voltage at 1.5 cranks per second.

Values of t / (RC), e^(-; t / (RC) ), 1 - e^(- t / (RC)) and V_source * (1 - e^(- t / (RC) ).

Your reported value of V(t) = V_source * (1 - e^(- t / (RC) ) and of the voltage observed after 100 'cranks'; difference between your observations and the value of V(t) as a percent of the value of V(t):

According to the function V(t) = V_source * (1 - e^(- t / (RC) ), what should be the voltages after 25, 50 and 75 'beeps'?

Values of reversed voltage, V_previous and V1_0, t; value of V1(t).

How many Coulombs does the capacitor store at 4 volts?

How many Coulombs does the capacitor contain at 3.5 volts?; How many Coulombs does it therefore lose between 4 volts and 3.5 volts?;

According to your data, how long did it take for this to occur when the flow was through a 33-ohm resistor?; On the average how many Coulombs therefore flowed per second as the capacitor discharged from 4 V to 3.5 V?

According to your data, what was the average current as the voltage dropped from 4 V to 3.5 V?; How does this compare with the preceding result, how should it compare and why?

How long did it take you to complete the experiment?

See if my notes allow you to complete the remainder of the experiment; if not, tell me what you do and do not understand and I'll try to clarify further.